In my opinion, the very most I would do is add an "Other" option, even then, it would be a lie of who you really are, stating who you feel you are meant to be.
This should be included in your profile description, as your gender is your gender, not your sexual orientation or "bodily changes", as who you are born as cannot be changed artificially, it's a lie to community and personally makes me sick...
And no, I'm all for eliminating the gender barrier, letting people be with who they want to be with (rather than just because they are of the opposite or same sex). But when you feel the need to change in such a manor, for absolutely no reason other than wanting to, there is no definite solution to do so.
Claim who you want to be, but if you're a trans-gender, this is a trait, not actual gender.
Of course this isn't my decision... So if you get what you want, I'll give you a derp face, here's a complimentary one
Yup... plenty more where that came from...