Well one way i can see this working out, and not affecting balance much, is to have Power boosters, and armour upgrades considered the same type of add on slot wise. So if you mount a power booster? You cannot mount an armour upgrade. So you are trading firepower over armour so to speak. So you can hit harder/longer, but cannot take it. Just an idea.
![[Image: overdrivetruckgoblin_zps191b1277.jpg]](http://i187.photobucket.com/albums/x238/ryoken12/overdrivetruckgoblin_zps191b1277.jpg)