Lemon - There do seem to be a lot more compact, rather than step through, frames on the market. I've also seen a few smaller riders using 24" wheel bikes to get around the size issue. They look like they should work on a normal carrier, but don't quote me on that!
Carol - I think you could be right in limited cases, but surely most sports combine enough skill/strength to be able to play to the limits of a range of individuals and therefore genders? Football I think is one that could be a level playing field. Not sure about racket sports, but could be interesting to try. Snooker, curling, golf, etc. and those kinds there really should be no separation.
I think the big difference is funding, if that were equal then I can't see any significant reason that would prevent women competing with men in most sports.