I think TIE is a great way to go. Of course it was my first choice, so I might be biased:) Start with the TIE Reserve Pilot which is the same as the Bridge Crew (IC), so this is a two for one costume, then you can add helmet, armor and chest box for a Tie (TI), Or different helmet for a Gunner(IG) and yet another helmet for a Navy Trooper (IN). The IC is also very easy to transport and take on an airplane for long distance troops.
Madighon