System based fleet defense and support

Systems upgrades designed to support a friendly fleet when fighting in orbit around it. They are not supposed to be able to take down adversary ships by themselves but work akin to "fortifications" used by friendly units. They are thus useless when the orbit is not contested and won't help against the ground battle phase.

These can feature : sensor array, warp in warnings, nano repair bays, orbiting missile defense. The effects may range from fleet shielding, in or post battle repair, salvos of torpedoes coming from fixed stations, bonus to some weapons.

To help war planning, systems fitted with this kind of active defense would have a visual indicator on the map, giving a clue of where space battles may be more or less favorable for the attacker/defender.