There are some problems with this idea. Developers should create new faces and names for the ladies, maybe it's a lot of work.
But I think that is a better idea than create a second server. As minimum, more realistic. Players that have a male team, would have the option to have a female team in the same league, like happens in real life. As it was talked before, new users leaves the game early because the difficulties of reach the same level than some players that have been playing for 6, 7 years. If the female teams are added, you create a new world to start all managers the same from scratch. As the female teams are linked to the male ones, the main game won't die, like it's going to happen if a second server is created. Also, Delft games could put themselves the femminist medal, and attract girls to the game. Who knows.