Stay with me as I try to articulate this:

Let's say the GM is going to create a space encounter.

1. They decide to use mass combat.
2. The PCs are in X-wings.
3. The PCs will have a series of objectives throughout the encounter.
4. The encounter will be interspersed with TIE fighters to serve as enemies.
5. One key objective is to disable or cripple an Imperial Interdictor.

How would the GM design point 5, give the PCs an avenue to disable the ship, without it boiling down to combat encounter stacked atop of combat encounter stacked atop combat encounter?

In a mass combat scenario it will be difficult to have not combat encounters. I suppose you might be able to:

1. Use/move terrain such as asteroids to damage and/or block the interdictor

2. Use social skills to convince nearby non-combatants to be involved

3. Land on the interdictor, spacewalk and/or board to disable/hack/destroy it

4. Find an enemy pilot they know and convince him to defect?

5. Trick another ship into blocking/ramming/diverting the interdictor off course

6. Lead enemy fire into the interdictor (being chased by missiles/torpedoes? Pull out at the last second! It always works in movies)

7. Search for an escape route through a heavy debris field? Lots of pilot and sensor checks here.

How would the GM design point 5, give the PCs an avenue to disable the ship, without it boiling down to combat encounter stacked atop of combat encounter stacked atop combat encounter?

Define this please. Generally Mass Combat is interspersed to a chain of combat encounters. Are you saying that you don't want that, or are you trying to avoid something where the players are jumping from starfighter to capital ship battery to boarding party?

First off, any starfighter/ship action encounter in this game comes in two flavors: a combat scenario (even if you take into account the encounter with the Interdictor in Onslaught at Arda I, it's just a combat scenario with the objective to run away), or a chase sequence (which can segue into a combat scenario).

So, from my POV, the best way to use the mass combat rules is to give the PCs an objective that influences the mass combat roll in various ways; capture those turrets, disable that shield, blow up those walkers, capture the general, etc. There is combat involved in all those things, but there are plenty of other things the players have to do besides (use Stealth to slip past the guards, use Computers to hack into the targeting systems, Mechanics for planting explosives, and so on). Boots on the ground scenarios is easy.

In space... choosing the objectives is easy. Figuring out how to build an entire sequence of linked encounters that isn't just the same thing over and over again is what I'm trying to hammer out.

Each phase doesn't have to be a single encounter, it could be multiple. With your example you could have 1 encounter as the PC's find a way into the Interdictor, and sneak into engineering, then another as the Tech sets the engines to overload and blow, while the rest of the party keep the Imps at bay or distracted. Then the final encounter is the getaway.

Now of course you could split the party up a bit. Perhaps only 2 board the Interdictor while others take out an Imperial Ace, and yet another group are trying to get more reinforcements from a nearby neutral party. You now have a Stealth encounter, a Star-fighter battle and a a social encounter all running at the same time (kept all on the same initiative track for ease). This lets the specialists do what they are good at, while giving you a chance to challenge them in ways that others in the party would normally handle.

So expanding a little lets look at the Social character who is trying to convince a local Pirate to help the rebellion out here, after the negotiations go down there may be a couple of minions waiting for them at the ship, its not a big combat, but it challenges them enough. It could also be a technical issue on the ship, but the point is its a low difficulty challenge that lets them use skills they don't always focus on. We have all had characters in a party where we have a little bit of skill in something, but since there is someone else with a better dice pool we don't actually get to use that skill very often.

SO for the series of space encounters you could have some of these ideas:

1. Navigate the firefight to reach the intended target, perhaps an Ace who is causing mayhem for the Rebellion.
2. A chase through a newly formed debris field after a cap ship explosion as the Ace tries to escape ending in the Aces destruction or escape
3. Re-grouping the scattered rebel pilots, giving the PC's minion group squadrons to help them
4. Final push to target the Command vessel, debris is now everywhere and laser fire too, piloting is tough, but they have the torpedoes and that ship need to be brought down.

On a side note was there a particular reason your choosing x-Wings? are all the PC's competent Pilot/Gunners? R2 Pc? Generally your PC's can get more out of a situation by teaming up in 2 seater craft, there are a lot of things that can be done in a ship, and having someone who can co-pilot, repair strain, shoot and provide leadership all while the pilot actually flies is a big bonus.

I'm conceptualizing. I do that a lot. The above example is non-specific. I'm having trouble describing what I'm getting at.

Basically, I want to be able to give players something they can do while piloting their ship(s) (not ditching their ships as soon as is convenient) besides combat and chases. Mass combat is where I'd probably apply it the most -- like I said, give the players a series of objectives that allows them to contribute in a meaningful way, but isn't just killing waves of Stormtroopers and TIEs.

On a ground combat scenario, it's simple to conceive objectives, and there are plenty of things the players can do to achieve that, but space is a bit more complex, as all the options end and begin with combat. I want the players to be able to disable the shields of a capital ship during the sequence, but I don't want to fall back onto the combat rules.

So i guess a good place to start is with coming up with a list of the different skills that can be used while in a ship to do things, a list of actions other than fly there shoot that. Its probably always going to include a piloting check, but that should not always be the focal point.

Computers: So you want to bring down the shields, perhaps a Slicing check to overload them briefly, but your craft needs to be really close, so the pilot needs to make some Average or Hard checks to stay close (with plenty of setback to get more threat from the roll!) while smarty pants in the back makes competitive checks with the defence system onboard? Of course you could just ignore the piloting part, but it would be fun.

Perception/Knowledge Warfare: There must be a weakness that can be exploited in the enemies plans, need to scout the battlefield as fast as possible, but of course that makes the piloting checks much harder, hope you have a good co-pilot!

Leadership: This is the idea of rallying the troops, coordinating their attacks, providing openings for bombers and the turbo-laser batteries. So your performing evasive maneuvers, then performing leadership checks.

Im still thinking, im sure most skills have at least a potential use.

Why not break the mass combat into sorties? You know, have the mass combat reflect the flow of days, maybe weeks instead of just the flow of a single furball?

That would at least give you more flexibility of mission type and details, which by extension will allow you to apply more options.

I mean, what if the sortie is to slip into the enemy fleet and stick target beacons on the enemy ships? Could you not make that checks like stealth, mechanics, computers and the like, even though it's being done from the cockpit? Then use the beacon count to generate modifiers to the mass combat check before running the next sortie?

Why not break the mass combat into sorties? You know, have the mass combat reflect the flow of days, maybe weeks instead of just the flow of a single furball?

That would at least give you more flexibility of mission type and details, which by extension will allow you to apply more options.

I mean, what if the sortie is to slip into the enemy fleet and stick target beacons on the enemy ships? Could you not make that checks like stealth, mechanics, computers and the like, even though it's being done from the cockpit? Then use the beacon count to generate modifiers to the mass combat check before running the next sortie?

And ship repairs become a much easier task.

I have to asume you have Stay on Target? its got some good ideas in the Dangerous Sorties chapter too.

1. Defending a Cap ship while it makes repairs to a critical system (hyperdrive, nav comp, major weapons system) using piloting to distract, jamming coms to disrupt the attacks, taking out the leader, spoofing missiles etc

From the X-Wing Video game (I think it was actually an A-Wing mission). One fighter squadron can run strafing and torpedo runs on the Interdictor's Shield generators (the globes above the conning tower), while the other runs air cover keeping the TIEs occupied. Once the generators have been destroyed you target the gravity well projectors and repeat the process until they all are done.

Encounter Idea:

"You finish off the last of the TIE's in your area when you get a call from HQ. Blue Squadron is in trouble! Blue Leader is down and the rookie squadron is panicking. They broke off from their zone and are only hounded by a pair of TIE's, yet they're on the verge of routing. Their only corporal, Blue 2 is trying to rally them yet he's not very good at it. Not to mention the pair of TIE's on his tail are taking all of his attention."

The players can use whatever skills they come up with to help. Gunnery to blast the two TIE's (wounding one will cause the to retreat back to their wing), Leadership to rally them, charm to calm them down, coercion to get them to settle the frak down. A computers check would give bonuses because they can override their ships systems (with proper slave circuit codes from HQ), or learn the pilot's names/backstory from looking into their personal files.

One more complication, when they approach they're told that Blue 7 has routed and a party member can use his superior piloting skills to chase him down. Then they can rally him back into the group with whatever checks they need (at a higher difficulty). The pilot is panicking and will try and land on an Alliance vessel without calling the traffic control tower.The hangar he starts heading for is full of a wing of Y's refueling. HQ will identify him as a risk and give the order to take him out if he gets too close. The PC will get one last social check. If he fails he will be forced to make the choice to take him out or not. If the PC accepts I'd just call it an auto-kill. The point is the moral dilemma. If he refuses, he will lode Duty and the AA guns will take the kid out. Poor dumb bastard.

Reposing the question (maybe this will illustrate my initial question better):

The players are in starfighters (let's say, some kind of bomber or Y-wing). They're flying into enemy airspace, and there will be TIEs and AA weapons. There primary goal is to bomb the power generator for the Imperial base. What would be the best way to design to bombing run part to be interesting?

For a slightly less combat-specific objective, lets pose the same question about dusting crops. How would that be designed?

You could use a Piloting check to determine whether or not the Pilot has the craft on the right course towards the target area. Then a Gunnery check for the back seater. However, the results of the Piloting check will determine the success of both the run up to the target and the fly away. If the Piloting check fails, the ship is on the wrong course and a Setback, or even upgrading the Gunnery check itself, could be added to the Gunnery check to incorporate the Gunner correcting for the wrong course. A success obviously means the course is correct. Enough Advantage means the whole is a breeze and the pilot regains some Strain. Enough Threat means the ship got to close to the fireball and the pilot suffers some strain.

Stay with me as I try to articulate this:

Let's say the GM is going to create a space encounter.

1. They decide to use mass combat.
2. The PCs are in X-wings.
3. The PCs will have a series of objectives throughout the encounter.
4. The encounter will be interspersed with TIE fighters to serve as enemies.
5. One key objective is to disable or cripple an Imperial Interdictor.

How would the GM design point 5, give the PCs an avenue to disable the ship, without it boiling down to combat encounter stacked atop of combat encounter stacked atop combat encounter?

Aimed attacks against a critical component like the hyperdrive and first coms to prevent reinforments. I would give such components some internal HT until they break.

Off the top of my head....

1. Targeted fire to key systems on the Interdictor to cripple it.

2. Have the party slicer (assuming they have one), try and slice into their systems to shut down key systems to cripple it. They have to stay within a specific range band to do this, so the pilot has to avoid enemy fire, while also staying close to the ship.

3. Have the party set up some kind of infiltrator ahead of time, someone smuggled on board to sabotage from the inside.

4. Have the party set up some kind of bomb as part of a shipment of supplies for the interdictor ahead of time, set to blow up and cripple a key system when triggered.

5. Trick the ship into chasing the party into a booby trapped area, loaded with ION weapons/mines, to cripple the ship if they are foolish enough to give chase.

Not strictly on topic, but: Lure the Convoy that is transporting the McGuffin into an asteroid field where a large ambush force is wating in hiding. While your friendly colleagues are harassing the convoy either destroy or get the mcguffin.

Space Combat is very much up to interpretation in this game and imo is most difficult to write interestingly.