I know that there were allready some complaints about there being no system defenses that actively fight enemy ships.



While I doubt such a mechanisem will be implemented due to it being a decent ammount of work, how about a different approach:

Make system defenses also give some bonus to your defending fleets.

After all, in an invasion scenario the advantage is usualy the attacker's - since he already has a ready fleet to fight while the defender has to scrounge up a couple of ships from wherever he can.

If the defender gets some bonus it might even off the odds, and deter half-baked invasions.



At any rate theres no doubt that defensive building that only slow the enemies conquest is not very interesting - most people want help to repel the invaders, not just slow them down.

Invasion really needs to be expanded upon from the "ground up" (if you'll pardon the pun). So many opportunities have been as-of-yet unimplemented, and for every one we can think of (planetary defense systems, orbital kinetic strikes, sabotage, more listed details on Invasion Strength VS Planetary Defense, strike teams, combat screens for invasion, etc), I'm sure the dev team has thought up ten times that.