The ISA faction in your mod has an unmanned fighter that always has a crew level of green due to there not being anyone in it to raise the experience level. That fighter is designed to be a next generation support fighter though so even with green CR its pretty effective, I suppose you could incorporate a fighter for every faction that represents a basic effort to produce an unmanned fighter. That would I think give you a viable mechanic to give each faction a total meatshield fighter craft. Have ISA's version as an early model of the fighter thats in the game currently (the name escapes me sorry) and have every other factions version as an attempt to emulate ISA's successful final model perhaps?