This just kinda flashed into my brainmeat, and I surely am not the first to think of it, but with the current meta being what it is, would allowing a "sideboard loadout" be a terrible idea? I'm not talking about having a pocket list that you can use if your counter comes up. You would still have to field the same ships in the same numbers, you would just get to swap out for prelisted upgrades that you registered at the start of the tournament.

An example would be registering at the start of the tournament with Vader with Lone Wolf, X1 title, Adv. Targeting Comp and engine upgrade along side 3x Tempest w/ X1 and Accuracy Correctors as the main list. I would also register my "sideboard" of the Opportunist and Swarm Tactics upgrades and another Advanced Targeting Computer. That way, I can fly the ships I want, and if I come up against something like say a Fat Falcon, I can put up a "soft" counter with Opp on Vader so that I can still keep it interesting. Likewise, I may choose to swap out Lone Wolf for ST and throw an ATC on one of the Tempests when I see Echo looming across from me. I just feel like this might give us the chance to fly the ships we want to fly instead of the ships that "beat" what our opponents bring to the table. Also, you certainly can't deny the extra tactical layer that it brings. That's two totally different styles of play for essentially the same list. Nothin wrong with that in my book.

What am I missing that makes this the worst idea ever vomitted onto a message board?

I'm fairly certain that the topic has been brought up before. That said, I think your idea has some merit.

Have come across sideboards in 40k, where players are asked to provide a core list (66.667-75% of the points) that they will always field, and are allowed to bring 1-3 sideboards (33.333-25%) that they can choose one of.

This works better with bigger numbers, I think the maths is poor in regular X-wing (but could be good for Epic).

The concept in the TCO (bring two squads, play with one until you feel the need to swap, then play that list until the end) is probably a better solution for regular X-wing.

It is often suggested but it really doesn't make sense in X-Wing.

In MtG you need to remember that those matches are three games long and the first game is ALWAYS done with the basic, pre-sideboard, list. It's only after that first game that you can make changes while your opponent may, more may not, do the same.

You also need to remember than in X-Wing things are far from the same. In MtG a card is a card and while sideboarding can radically change how a deck is played the number of cards is the same. In X-Wing you are looking at points and there things are NOT the same is a vast number of cases. You may say "must keep the same ships" but with that limitation I should still be able to change pilots along with any upgrades.

When it comes to "immersion" the idea of a sideboard doesn't make as much sense either. You may have an idea what your squadron will encounter (the metagame) and try to prepare accordingly but by the time you actually engage (start the game) you will not know for sure what you'll be facing but at that time it will be too late to make changes. I've read discussions mentioning 'unknown' load-outs for ships and they make more sense except that even those shouldn't allow changing the load out.

In X-Wing a side-board like concept that may be workable is a two-list game. One way of doing it is mentioned previously but it can go a little further. An idea is that you bring two lists to the tournament and at the start of each game you hand your lists to your opponent which he does the same. You both get a short time to look at the other person's lists and secretly choose which of your lists you will actually play; the chosen lists are simultaneously revealed and play progresses as normal. Now what those two lists look like can be debated and may go from any two formal legal lists (like say Fat Han and Phantoms) all the way to two identical list (really one list) although restriction could be included making the list at least somewhat similar.

I suppose I should have clarified that the pilots would have stay the same as well. Same ships, same pilots only the upgrades, the " loadout" is changed.

Thematically, I don't see a problem either. Either these encounters are one off battles, where the Imperials set out to hunt down the Rebel/Scum or vise versa or they're long campaigns where most of the Imperial fighters would need a support ship to get them to the playground in the first place. Either option thematically offers plenty of time to perform a quick and dirty pit stop.

The two list option is fine, but the point of my idea is to NOT have to have a hard counter list in your pocket for when the "Rock" comes up against your "Scissors". If you think critically before hand, you don't have to fly ships you don't want/aren't used to.

If you can stop to change any of the upgrades slots there would be no reason you couldn't have one pilot jump out and another take his place at the same time. At least that is my philosophy when when it comes to allowing changes to be made to a ship.

I very much disagree with the idea that you could have "plenty of time to perform a quick and dirty pitstop" once the battle has begun. Most ships in this game are hyperdrive equipped and the few that aren't really wouldn't have a lot of time to evaluate the approaching enemy force before deciding what to load and then launch. In a lot of ways changing pilots would actually be the easiest way to alter a ship as that is just changing who scrambles to which ship.

With the two list concept you may need to re-evaluate. For starters just because there are two lists and I believe those lists should be anything legal doesn't mean restrictions could not be put on the lists. A relatively simple one might be to say that both lists must use the same models which can leave you with a lot of options but actually cuts things down to your sideboard idea quickly.

As for the two list idea allowing a "hard counter list" you again need to re-evaluate. Remember that this works both ways; you have two lists that you could use or face so choose wisely. In the Rock-Paper-Scissors version maybe you want to play Scissors but what is your second squadron going to be? Now the opponent you are going to face shows you his lists and you see he has Rock and Scissors; if your second list is Paper do you play that assuming he'll play rock for an easy win but knowing you'll be sliced if he plays Scissors but if your second list is also Rock then do you play for the balanced game or easy win by picking your Rock or do you go with balance or loss by picking your Scissors? It may not always be that easy especially if you throw in Lizard and Spock but the idea is still that you have a guessing game to play when the battle starts as to who is actually going to show up.

The main problem i do see with this is to decide who gets to pick his sideboard last. Because that player will be at a definite advantage.

Or do you just get to look at an opponents List and Sideboard and then decide your loadout in secret. I would see no problem with that, it would just take some time to switch out stuff and check if everyone's list would still be legal. So that would very much complicate tournaments and could potentially lead to serious messups!

The one real possibility i would see is the system they run in Warmachine/Hordes.

It's a long time since i played it, so i don't know exactly how it worked, but basically you choose a faction and bring 2 lists (or 3 depending on the tournament format i believe) Then depending on the swiss round you play, you get to pick your list before or after your opponent. And you have to play each list you bring at least once in the tournament as far as i know too.

In Warmahordes of course things are a little different because there are 10+ factions and each list heavily relies on its warcaster or warlock. So for X-Wing you could only field any named ship once in all of your lists probably.

I see multiple lists as the only practicable solution for X-Wing really...

That's precisely why it's a quick and dirty pit stop. This pilot is assigned to this patrol, and he/she has just enough time to refit their bird before flying again. Also game wise, another pilot is another card entirely. It's not the same list.

As to the second point, all the lists and side board cards would be registered before the tourny, so any illegal shenannigans could be sorted out then, like they have to be already. Then yes, you'd get to see all of your opponents options and quickly load you squad out with your best guess and then fly.