I've whipped up a small mod to add a basic faction system.
http://s94941683.Onlinehome.us/Campaign 1 - Homefront ROL.zip
The Terrans and Abbidon will now brand you as a criminal and shoot on sight if you kill enough of their ships. The infractions are broken up into Base, Heavy, Medium, and Light catagories, with the number allowed before you are outlawed going up each time. You kill ONE base and they'll be after you, but sats and fighters are much less stringent.