The more I think about it, the more I think this would be a good idea, but only in a specific sense.
I think the way to do it would be to create a number of female models of decent quality (do it on the cheap, outsource it) and just use the bone structure animations from the core FIFA title. Like someone previously mentioned, licensing the teams would likely be super cheap. Drop the models into the existing FIFA engine and release a stripped down game for $20 digital only.
If it sells, the market is there, go nuts. If it doesn't, not much was lost. As a side benefit, EA gets to double dip on the crazy FIFA fans that want it all and they can entice people on the fence about soccer games in general with a cheaper alternative. All the super meatheads that refuse to play as women wouldn't be buying it anyway and they'll have their un-sullied sausage fest to play with in the core game.
If they made it DLC for the core game, you're asking the interested market to pay more for something that is niche anyway. Why not try to lure them in with a cheaper alternative?