There are several problems. Most tissue transplants have to be genetically matched otherwise the the recipients immune system recognise it as foreign and rejects it. If anyone wishes I can expand on how. So, when we do kidney, bone marrow, heart lung etc etc transplants we have to have a very good genetically matched donor. There are very large international data bases of potential recipients for these. Potential donors can then be matched quite quickly.
I know of no database for penis recipients.
So far the transplant organs that have been successful, need little nerve tissue integration. Kidneys, hearts, livers, endocrine organs can function without a lot of integration (although they do normally) into the nervous system. They can bypass a lot of information because they are linked and dependent upon the blood system.
A Penis and Vagina are different. In MtF the surgeon 'saves' the nerve end connections that make a penis respond to orgasm and keep it in the neo-clitoris. In transplanting a penis to an FtM the nerves cannot be connected, nerves once severed don't grow back, without some very new technology, which is promising but forget it as far as sex reassignment is concerned. The erect penis is dependent on a blood supply to get it erect. This in turn is dependent upon the nerves that allow stimulation. If the nerves don't exist there are problems.
There is another problem that the public don't always think about. Having any sort of transplant is usually an enormous emotional crisis for the recipient. There are often a host of guilt feelings.
In the case of sex organ transplants this may be incredibly magnified. At the moment if I could have a vaginal. uterine and ovary transplant I would love it. If/when I got pregnant, whose baby am I having?
In the case of a penis transplant is this the same, BTW do testicles come with the penis? and the prostrate gland? If not the thing may be a bad substitute for a strap on.
Of interest there have now been two face transplants. The latest was last week. Both recipients had terrible facial injuries but were otherwise healthy. I think one had her face torn off by a dog, the other due to an explosion. Both are going to need incredible counseling. They will never see themselves in the mirror. They will always see the person who donated the face.
Sorry if I have upset anyone, didn't mean to be morbid. I'm fascinated.