Personally, I would like a concept based around a neutral faction, maybe mercenaries or just a normal run of the mill family, much like X-wing Alliance, where you are slowly absorbed into the larger conflict around you, forcing you to take sides in the Civil War.
It would be splendid to have, like in Jedi Knight, a choice to go light or dark based on your actions (kill friendlies, not completing certain objectives, bailing out of missions, etc) and from there modify the storyline accordingly. Of course its a hell lot of work and not up for consideration. Still, I would rather fly pirate or rebel. I'm an Imp by heart, but from my point of view its much cooler to look at the Empire from the outside, as an evil, overwhelming military faction, than from the boots of a normal buckethead.
Flying rebel makes you feel more heroic, and I think its a feeling we want to rescue in this project. In TIE Fighter, I felt more of an expendable asset rather than the crucial game piece in X-wing. As I watched my TIE buddys die I said to myself "whatever, the ISD has a lot more squadrons where those came from".
Flying pirate or neutral combines a bit of both.
Flying Imp is cool, but maybe JUST for certain occasions. "Your group just captured several TIE interceptors and need them to infiltrate the perimiter around a Golan Arms platform to inspect bacta containers"... or whatever. You get the point

Thanks for reading