Is it possible to cancel or drop some members out of a fire team to use impetuous orders this members would have if not in a link team?
You can't just choose to drop a member from a fireteam. However, you can cancel the whole fireteam at any time without any expense. You can also form a new fireteam, using some members of the old fireteam, but this of course will cost you a command token as per the usual fireteam formation rules. So, if you choose to cancel your fireteam at the end of your Reactive turn, you would then generate any impetuous orders they might have at the beginning of your Active Turn.
Though it's an edge case (even more so because it needs to happen over two of your turns), you can take advantage of the rule that allows you to add members back to a fireteam for free and also take advantage of their impetuous orders in this way: Have all members of a FT dodge an attack against them on the Reactive Turn (this would likely need to be one of the last Orders spent in your opponent's turn, and your FT would need to be spread out enough). Have your Impetuous models dodge away from your team leader enough that they become out of coherency. They will automatically break from your FT without the FT cancelling completely (as long as the team leader and one other model are still in coherency and not in a null state). On your next turn, they will be Impetuous and you can use their Impetuous orders. You then need to engineer a situation where those Impetuous troops are once again in coherency with your team leader at the start of your NEXT turn, at which point, you can add them for free (and lose their Impetuous Order). Honestly, now that I've written it all out, it doesn't seem worth it to actually try to do this on purpose. Just keep it in mind if a similar situation ever arises on accident . Nevermind, I can't read.
In order to automatically rejoin a fireteam that a trooper left due to coherency, it has to happen on the next Active Turn. So in your example they would not be automatically rejoining, since you delayed for an additional Active Turn.
