Here's an utterly fantastic idea that combines aerospace and BA centric ideas :
Boarding action!
Two warships in space. Dropships ferry BA, maybe even mechs or vehicles (unlikely) between two warships. Inside the warships are corridors where BA will largely have access.
Just think if you could make the dropships pilotable... like big, fat aerospace with turrets. That's just frikkin' awesome.
Naturally, aerospace would dominate the area in between.