Considering all of the gender surgeries available, I don't think this is question is too far out of the mainstream.
However, rather than a pelvis transplant... with all of the risks of rejection, etc., you might want to look at what is happening with 3d printed bones. Japan has already had some success in replacing injured vertabrae with 3d printed vertabrae and research is continuing into bones that are printed and then seeded with your own cells so that they are indistinguishable from your own tissue.
Someday you might be able to get 3d generated bone that can be grafted to your existing pelvis to give you the shape that you want. Or if you can't wait for science... there are silicone hip implants you can get right now.
That being said... Surgery is never something to be taken lightly. A lot of gender surgeries are still fairly experimental. Even with the best surgeons you might not like the results. And there is always the possibility of disfigurement or death. ...but if this is something you feel driven to do you might not be worried about that.
At the risk of derailing your desire for wider hips... if you are looking for surgeries that are going to enhance your passability or quality of life you might want to look at Facial Feminization Surgery or the Yeson Voice Feminization Surgery first. You can always pad your breasts and hips, but your face and voice are always out there for the whole world to see. You should look at that before chasing after anything that is too new or radical.