Q:
Does the "turns to wait for next attack" make them assemble a fleet, or just control how often they will send in a lone ship?
I'd like to see the AI take what it knows (i.e. has already seen about the target's defenses) and assemble a fleet that can take them, and not come back until they have that big of a fleet. Otherwise, they are just wasting ships. If I hit an enemy planet, and it was defended by several WP's, I certainly wouldn't go back there without a fleet that could take those defenses. Of course, the defender could further beef up the defense while I'm gone, but it is assuredly not very likely to weaken them. I'd use single ships to probe for recon, then assemble a sufficient force to take the defenses I detected before I launched an actual attack. If I sent a single ship in to an enemy planet and found it too heavily defended by immobile forces (WP's, satellites, bases), I'd just sit outside their weapon range and click "end turn" 30 times, then go home & get some friends
It should be a simple set of rules to make the AI do likewise.