It seems to me that the ai progress from killing warp gates is too high for the benefit(disregarding the fact that most people seem to kill them by habit, as taught by the tutorial). I find that with my playstyle(never take adjacent planets, pretty much only take a planet if its an advanced research, an advanced factory near the ai homeworlds, or a necessary intermediate planet on a long path(~5 hops away from an owned planet) to one of the above), it is by far the ideal strategy to just ignore warp gates even on planets I take anymore. Removing the chance of waves at those planets would cost me at least 40 ai progress(from raiding adjacent planets). I know I'm somewhat atypical in playstyle, but it really seems to me even with a normal playstyle, it often doesn't seem worth all the extra progress. It also seems that the ai seems to like wasting its reinforcements to reinforce warp gates on my planets, which just means free kills for my turrets and means lower general ai unit production.
As an example: My current game has had its ai progress vary between 40 and 60(even though the number of data centers was lower than what I've usually been seeing), I've taken 4 advanced research labs(and am currently in progress of securing the 5th), 1 advanced factory, I'm within striking distance of both homeworlds, and have gathered enough knowledge to unlock tier 3 f/b/c, antiarmors, mirvs, and munition boosters plus spire/raider starships and most tier II turrets. This doesn't even need really any sort of really deep raiding, merely being willing to not take the 1 or 2 planets between "interesting" planets, not getting bogged down killing everything in adjacent planets(thus hitting planets that are not alerted, and are relatively weak) and being willing to use enemy planets for energy generation(mkII plants).
All that for this suggestion: change ai progress from warp gates to 5, and enemy command centers to 15. I don't think it will change the game much for people who actually play "normally", but make my playstyle slightly less broken(honestly, its at least close to as broken as the deep raiding playstyle was--10 ai progress for 10k+knowledge +a special building, makes it way too easy to keep the progress level low(3 data centers easily cancel out 2 planets and the time to take them even at 1 progress per 5 mins)--15 per planet would at least make me more likely to at least hit tier II enemy units in waves after I take out one of the homeworlds).