What tissue would they use for the phalloplasty?
They will be using any tissue they can think off. Inside or out.
Surgeons are experimenting all the time, remodelling bodies when faced with mutilating tumours or trauma.
This is particularly relevant for military casualties.
Where there are planned interventions there is the potential to use donors or synthetic prosthetics or even animal parts (think of the use of pigs valves for heart surgery).
But there is the problem of rejection which then requires the lifelong use of immunosuppressants.
Therefore using the patients own tissue appears to be the solution, hence the use of military field hospital surgical expertise.
Back to planned intervention on healthy people, surgery is not an exact science.
Many people who undergo operations of any sort often have to return so it can be tweaked and revisited even in a minor way.
This is quite normal to expect.
Any gross removal of body parts is a process trial and error where a favourable outcome only might be possible. When it is being done on a healthy person the outcome, in theory, should be better.
But complications happen and everyone involved has to keep going because the perceived problem has now turned into a medical nightmare.
And here we are, experimenting on healthy bodies.