AI is totally hardcoded save some values you can toy around with in terms of priorities in gameplay.constants. What you ask isn't really possible. Feeding them money via hidden researches might encourage more ships being built, but that's about it, really.
In Ret the AI had insane free money but you still saw maybe 3-4 capitals at a time unless they turtled for an extreme length of period, but I never saw them even approach the default cap.
/e
Now that I think about it, I think you can get the AI to spawn units via abilities. I'm not really sure how all that works, though. I think it might involve more hidden research stuff. Maybe someone else knows...