http://www.shrapnelgames.com/ubb/For...ML/003500.html is my mod take, though I've concentrated more on moving stuff around in the tech tree and adding improved ship sizes.
Quick AI note: you'll have to re-write EVERY AI that you want to use this mod. Worse, if you want the AI to use mixed fleets, you'll have to do quite a bit of gymnastics with the files, and even then there isn't a lot you can do to make the AI build the right number of each kind.
Phoenix-D