first off are there any build tools for modelers to make new ships?
my excellent idea...
there need to be 3 rebel transports (see empire strikes back/ the first transport is away!!!! is already in the game) and part of your mission success is making sure they evacuate. that's where your x-wings/ties come in.
the transports act as spawn points until they take off. getting 2 away is a required victory objective for the rebs. 2 destroyed automatic defeat.
if the map is made alot larger it could work. the x-wings and soldiers have to protect the transports as a first priority and then destroy the at-ats. but you have to decide how much time to spend doing a little of each to get by.
on the other hand the tie-fighters try to sneak past the rebel's hardcore cannons to fire on the transports.