i'm not going to deny that it is very hard to catch up with the BB veterans, as you pointed out. however, the problem you speak of will arrise again in 6 to 8 seasons, since by then the womens BB will have their own veterans, not to mention that the BB veterans know how to train their players, and thus, they'll most likely be at the top of the game again.
Also, a few other contradicting things:
as for the ecomony, if you are going to have split economies, it would be like having 2 different teams. they'll then need different staff aswell, and so on...
So basically, if you'd add a womens BB, it would be the same as if you'd have a second account on the game. cause econmy is split, staff will be split ( can't pay staff with mens economy if you split economy), players split etc...
basically, you would need a second BB game in it's whole. Like i said before, ir eally do like the idea you have. but at this current time, i really don't see how on earth you could fit it into this current BB game
what might be an alternative is this:
have a supporters feature, that would allow you to show all the men to women, but keep the same stats. all that would be required to change then would be the picture of your player, and their names. i'm not sure how much work it would take, but i think that it should be relatively easy to implement an extra name (girl name) to each current existing player. Thus, you'll be able to see them as womens on your team, and when you look at the other team, you'll see the other teams players as women already.
the only annoying thing then, would be if you sell a player, you'd be selling it to someone else, and for U21/NT teams, they'd have a hard time scouting, cause if they mail around for the mens name, and you have your settings so that it would show having a womens team, then you'll be giving the U21/NT teams rather unpleasant extra work load... (and communicating about players wouldn't just be a U21/NT thing. sometimes players mail eachother to hear prices for a possible transfer etc... --'remember, if you get reported as spammer, then you could be in for some trouble on that ;) i don't advise doing so, but some chose to do it -- so those too will have a harder time...
each suggestion has it's up and down sides.
now, the idea about a clean sheet, i'd suggest you discuss that in another topic, cause this one is about the womens BB ;)