did another test with two Alliance AIs in a resource rich system. The game got problems after ~2h play.
Some things I learned when checking the AI play by "watch" function:
1. The AI does not build more than 4 capitals
They had lot's resource, capital support points maxed out. I had removed fleet support from capitals but still they would not build more than 4.
It looks to me that the AI does not recognize ship class at all beside colonizer. It sends any ship, including high ranking capitals, on all sorts of mission. So maybe they simply limited the number of capitals to stop the AI wasting resource on them?
The spawn function does not look for capital support points. What I'm thinking now is to have capital shipyard spawning all sort of capitals, and have more and improved spawn functions by capital (and maybe fleet) support research?
2. The game had problems when a ~200 ship fleet activated gravity entrapment. About 100 frigates and some cruisers had this ability. The game would freeze for some seconds and run purely for some time after it. Either the graphical effect or something in the game implementation of this makes problems.