Alright, so for a "Nemisis battlegroup" I'm looking at a Lancer, 4 Imperial Refit Gonzanti transports, 2 Intercepters, 2 Bombers, 2 full minion groups of Tie fighters, and 2 half minion groups of tie fighters. The tie fighters being easilly replaced between scenerios, and surviving tie pilots "promoted" to intercepter if the advanced craft get shot down.

As the PCs get stronger, promoting one of the tie minion groups into another two intercepters and two bombers, giving the force 4 intercepters, 4 bombers, a 4x minion group, and two 2x minion groups. If the PCs can kill a transport, they get extra duty, but the transport gets replaces quickly. (the lancer, on the other hand has a name and persistant HP, but the PCs have persistant torpedo counts, so I expect it to remain a boogieman for awhile.)

So, I'm brainsorming various things a party of fighter pilots can do with a squadron of Y wings. If you have an ideas, feel free to add them.

Why reinvent the wheel ? Since Lucasarts has already done all the leg work for you, just shamelessly steal their missions.