I am unsure exactly how they would behave. The only hardcode I know of that people stumbled on is that the AI maintains a frigates : capitals ratio, ie for a certain number of capitals it has a certain number of frigates.
This was discovered when someone tried to make a mod that made capitals hard to get, and the AI got stuck dead in the water because it couldn't expand its fleet.
Making them easier to get most likely won't hurt the AI. If he doesn't build much in terms of frigates, you could always expand the fleet point gains from each research rank and it will probably straighten them out.