Like the topic says: what if you could build NPC spawn points and place them around gamma bases? They wouldn't drop any loot and would follow the same rules of engagement as turrets. You could place different factions, types, and levels of bot, so there'd be plenty of potential to upgrade and tweak. Including respawn rate, aggressiveness, and engagement radius maybe?

Obviously this wouldn't be a substitute for actual defending players and turrets, but it might be useful AND it would make bases feel bustling and lively.