Bi-annual is still alive!
On AndrewChristlieb's ideas:
Perhaps this dilemma can be accounted for by fighting multiple rounds per interaction? For example, when the squadrons interact, the attacking fighters are forced to attack the defending fighters first (skip this round if there are no fighters). Resolve this round, remove destroyed fighters. After the initial fighter round, players now pair off fighters with fighters first but if there are 'spare' fighters these may now attack the bombers. Resolve this round; any leftover markers are treated as per the rest of the Warp Rift experimental rules. Example: 5 Fighters (5F) and 2 Bombers (2B) attack 2F and 4B. Resolve round 1, the 5F attacking the 2F defending and leaving the bombers alone. If, for example, one attacking fighter is destroyed, the resulting waves are attacker 4F-2B, defender 2F-4B. Now round 2 is resolved. 2 attacking fighters must now attack the two defending fighters but the other 2F may attack the defender bombers. The defender cannot attack the attacker's bombers, however, because all of the defending fighters are already fighting. Resolve this round; for example, the attackers may lose 3F but the defenders may lose 1F and 3B. The waves may now move away as normal (I think that's what it is).
This is essentially a 2-round combination of ideas 2 and 3, with the exception that in the 2nd round, fighters must still be assigned to other fighters before they can be assigned to bombers. This would mean that bombers would have to be quite weak compared with fighters to allow the excess fighters to effectively defeat them regularly.
Otherwise, as I suspect might have been the intention, bombers simply lend their firepower to the fight, and any destroyed ordnance must be fighters first, bombers after. Thus, if in the above example there were 4 casualties for the attackers and 3 for the defenders, the attacker would remove 4F and have 1F-2B remaining, but the defender would have 0F-3B remaining. This would necessitate the taking of saves after casualty allocation, however....
Thoughts, anyway. Thinking Stone