This a Qustion more for the guys who like modding the game as I do

Can other races be added to the game and if so whats a the limit to them

Im currently working on a mod based on the a book series by David Weber called The Stars At War. there are Nine (9) differant Races using simlar Tech that I would like to Add but do not as of yet have the expairance in modding the game to do so. Most of the things I need are there and the game is very simler to the books in many ways but I'm stuck and need some help