Well, if we had the technology to transplant a uterus the it's reasonable that we could also transplant testes. I know in mtf SRS the penis is used to create a vagina but the erectile tissue isn't. Lets say that that erectile tissue could be used to create a more realistic penis for a trans guy. So if the transplants are possible you could match up a mtf with a FtM. Then just exchange the tissues to be transplanted.
Julia