I would like to repeat my position that if we humans are allowed to stack ludicrous amounts of defense on one world (like our HW), then why shouldn't the AI?
Remember what the builder hybrids used to do? 
And to be honest, I didn't mind that. If I gave the AI a clear chokepoint for long periods of time, and I let the AI build up on it, then that is my own dang fault.
IMO, the problem was more of the rate of the buildup rather than the fact that they could.
As long as post game seed accumulation rate is fair, and the AI does not get to "cheat" "costs" during build up at game seed, I don't really mind.
