And while we're on the point, I have to say gate raiding is the most glaringly hole in the wall feature I've seen in strategy games for some time.
Yes, that one is actually intentional
It's negated by CPA waves, though.
On the other hand, as you've now found, CPA Waves + Schizo Waves is actually easier than having neither of those options (or neither), since it disrupts the AI's concentration of force. That's one area where we might be able to make a change, by having a quasi-schizo modifier that tries to pick like-speed-ship-types from its available set and group move them until it reaches human territory before un-furling. There would be some exploitability problems there with ambushing and lightning warheads, but probably nothing worse than CPA waves in general. And even if exploitable, it'd just be a modifier for those desiring it, and could be fixed (or possibly just scrapped) as needed. Of course, I'm not sure how Chris feels about the idea
On the infrastructure stuff, one of our planned alternate endgame scenarios ("plots") is to have special AI structures scattered throughout the galaxy by the destruction of which you can cause the AI to shift towards a more aggressive stance, which could be accomplished by applying a modifier to the border aggression cap. Basically a galaxy-wide version of smashing up guard posts and command stations to get the enemies to come after you. The balance will be a little tricky, probably buffing the AI core world defenses to make some degree of it necessary, and having the individual structure-destructions result in a fairly significant AIP boost, etc, so that it doesn't just make the game easier... anyway, you might find it more to your liking.
For a similar plot, or perhaps instead of (still working it all out, maybe they could work well together), I'm hoping to implement a sort of "Showdown" plot where once you're on a more-or-less even footing with the AI (either when you destroy the first AI home command station, or something like that), it basically makes an all-out attempt to kill you, and if you survive you can probably win in an hour or less. The idea is, for those who want this, to condense the challenge of that second half of the game into one really intense series of battles. The design challenge there is manifold, in that simply freeing all AI ships to attack will basically kill your framerate, and even aside from that there are many players who set up such effective defenses that this would be suicidal behavior on part of the AI. So either it would need ways of bypassing normal defenses (spawning new exo-galaxy wormholes, special siege-weapon type units to smash stuff, etc), which I personally would find frustrating (not the end of the world), or we'll need to find some other way of making sure it's still fun.
Back to the infrastructure thing, I think it would be possible to have a sort of minor-faction-type-event where instead of "Mining Golem Going to Pwn Murdoch in 1:34:22" it's basically "AI 2 Finishes Construction Of New Fabrication Complex in 0:25:00", and when they finish it they get a new bonus ship type, and when you destroy it it goes away. This wouldn't change the basic AI behavior, it would really be just as much a surprise to it as you from a code perspective, but it would provide a new "mission type" for the humans to go out on, and give you a way/motivation to strike at the AI infrastructure without reducing the difficulty (to make it a little less one-sided, the destruction of the complex could reduce AIP a little, or maybe the humans could use it like a core fabricator, etc).
Anyway, I think that's enough from me right now