If a player wants to cover or over watch the group or cover an area, how do you handle the turn order?

Player wants to cover an open area. On npc action two scout troopers pop out an are going to engage party. How can the player covering the area take action to protect the party?

There really isn't an "interrupt" or "on hold" mechanic in this game. You could make one, I suppose, but I don't really think it would work out that well. Fortunately, there are other tricks you might try.

First off, a character who regularly tries to protect his party should look into talents for that very purpose. The Tactician (and others) have a talent called Bodyguard. For a maneuver, they can upgrade the difficulty of attacks targeting an engaged ally. It's pretty simple to say, "As Duke Slytalker takes aim, I start laying down cover fire. I'm going to spend a maneuver and strain, and anyone attacking him upgrades the difficulty." If those red dice cause the attackers to fail at their attack rolls, they just weren't able to take an effective shot. If they cause a bunch of Threat or Despair, you could say they got hit by the cover fire, taking Strain (remembering that Strain and Damage are basically the same when inflicted on Rivals and Minions).

I also have a loose rule (more of a guideline) at my table that a player can use a skill to try to increase the difficulty of another characters checks. For example, if a player wanted to sprint across a battlefield, dodging and weaving to avoid blaster fire, he might say, "I want to make an Athletics or Coordination check. Serpentine! You can't hit what you can't see!" He'd make his check, and with one success, all attacks coming at him would increase their difficulty by one for a round. With three successes, it would be by two, maxing out at five successes to increase it by three. He could spend Advantage to gain Ranged Defense, and so on. I don't have this as a hard and fast rule, because you'll need to adjust it as the situation calls.

So, using this guideline, the player could say, "I want to use my action to lay down cover fire. I'll make a Ranged attack roll, but I'm not really trying to hit the enemy. I just want to keep their heads down so they can't shoot my buddies." Using those guidelines, he might use extra successes to suppress multiple targets. And, of course, if the enemy rolls a lot of Threat, you could say that he popped his head out at the wrong time, and got hit by a stray shot.

Yeah mostly it's covered by the initiative system and a PC being able to use different slots in the sequence each round. Going last in one round then first in the next is a great example of waiting for the right moment, then laying waste to the enemy. I understand it's not perfect, but to loose that small part we have gained so much more.

I like the laying down fire to upgrade the difficulty, failures cancelling shots, threats causing duck back going prone, and despair equaling a hit. Thanks so much for the great ideas!

There is a talent in the Warleader (Guardian splat book) called suppressing fire. It allows any ally within short range of the Warleader to spend 1 advantage on a missed attack to inflict 1 strain (per rank in talent).

So you probably want to make sure your not doing something more powerful than that.

There is a talent in the Warleader (Guardian splat book) called suppressing fire. It allows any ally within short range of the Warleader to spend 1 advantage on a missed attack to inflict 1 strain (per rank in talent).

So you probably want to make sure your not doing something more powerful than that.

I wouldn't worry too much about that talent, as it does something very different, just with a similar name. The talent is, "I missed, but I have some advantage, so here's something extra I could spend it on." They really don't seem to step on each others' toes.

In this scenario, has combat started yet or not? If, in anticipation of the arrival of those scout troopers, your player said "I'm going to lie down in over watch and make sure anything that anything walking into this clearing regrets it", I'd give him a free shot (not full turn) at the beginning of combat, or at least a bunch of boost die to his initiative to represent how, in his mind, there was already a fight started. Once, I even let a player choose between Cool and Vigilance for initiative, whichever was better, to represent his superior positioning as combat broke out.

It should be noted that my usual GM-ing style is loose, and I have little concern for overpowered scenarios as long as it tells a good story, my players have fun, and the party doesn't complain if I throw something big and stupid at them (or railroad them a bit for the sake of the plot). So, my words: grain of salt. But if a player takes great care before battle to get the drop on someone, I feel like that should be rewarded. In one scenario, the players came upon a protest - some guards were forcing a group to deface a thing, and people had gathered to boo and hiss. The players wanted to stop it quickly, and one player (the sniper) climbed into a good position and drew a bead on the guard captain while the others pushed their way to the front of the crowd. They were waiting for the right moment to stop the thing, maybe debating if they wanted to talk it out, when one of the guys refused to keep working and the captain drew his hand back to strike the worker with a weapon. My players said "I'd like to take the shot now." So I let him; I even gave him credit for having taken one or two of the Aim maneuvers, since he was all set up and basically staring down his scope at the guy. Then we rolled for initiative.

Alternatively... has combat already started? That's trickier, and comes down to whether or not you want to make a house rule, and whether or not you want to strive for good game balance. I prefer the narrative to the mechanics, and I'm ok breaking the later for the sake of the former, so if my player says "I have my blaster trained on those guys in cover, and if they make a move I'm taking the shot", I'm willing to have that be his turn and give him a shot with no cover if those soldiers break into a run. It's not the best solution, in all honesty. Maybe implement something similar at the cost of strain? Or, you can always narrate the scenario back to them and make them see they're better not taking the action, so they make the decision to drop it on their own. Maybe say "yeah, you could do that, but there'd still be a setback die because they're moving so fast and you either have to track them as they sprint or have a near-perfect reaction time. It's the same either way." Then see what happens?

There really isn't an "interrupt" or "on hold" mechanic in this game. You could make one, I suppose, but I don't really think it would work out that well. Fortunately, there are other tricks you might try.

Actually, there are interrupts... but they're buried in the feat trees. Most of them involve spending strain or destiny. There is no "free interrupt" ...

Some examples include Hold Together & Mental Fortress... which can be applied out of turn.

That all said, the easiest way to deal with interrupting is to require a destiny flip for dumb luck slowing them down.