In F3 you can change your face in Rivet City. How about changing your gender, too? It could be a successful surgery, or it might turn out to be some rush job. Is it in NV?
I thought that that option/ability from the Scientist/Doc in the Bow of the Carrier by Rivet City was pushing it a bit too far, as for him to be able to do that successfully he would need a sterile operating theatre and all the gubbins to go with it.
Also why would we want to change our gender other than to try to gain access to something we may be barred from due to the characters chosen gender, that is something you can do in a replay. We do not need to be able to do everything in a single playthrough, personally I do not want to be able to do everything in a single playthrough as that limited the replayability value in my opinion.