modular multi role would be the pentagons wet dream, the reason it doesn't work for planes <well....... it does..... to an extent>
okay, the reason it doesn't TOTALLY work for planes is they are limited by air frame, an f-22 can't pull awacs duty because it just can't have that gear and still fly like they want
in space that is less of a problem, all you have to worry about then is engine power and fuel consumption, then it's all economical
build lots of cheap multi role fighters <mini awacs\bombers, fighter\intercepter\stealth> just swap engine pods\armor plating, have the perseus A, pers B pers C, slight if any cosmetic variation, different electronics and engine pods, have identical chassis for the three and modular pods being the only real variant