Those are definitely intelligent questions!
The use of a section of the sigmoid colon does not involve any smell. The scent of excrement is produced by the E coli bacteria which inhabit our lower gi tract.
As far as I know the best known docs are all using a relatively new penile inversion procedure using the extra section of urethra as part of the neovagina and yes, that affords some lubrication on arousal (precum comes from two different sources and one purpose is to change the pH of the urethra to one that's hospitable to sperm).
I believe Marci Bowers uses this method now, the new team at Boston medical center also and probably also the surgeons they've been observing in preparation. I believe Satterwhite also and I'll be verifying that when I have my consult with him next week. I don't think there's additional cost, the amount of extra work is quite small.
Normally not all of the skin on the testicles is used for the procedure and yes the PI technique gets a lot of its depth from the length of the penis. Average size before should get you 6" depth post op. A neovagina does not lengthen on arousal so depth can be an issue (addressable by choice of sexual position).
As far as I know the current WPATH does allow for any of the normal prerequisite to be waived if medically necessary as determined by your psychologist or psychiatrist and PCP. Estrogen carries far less risk when taken transdermally or by intramuscular injection, FYI.
Getting criteria waived may be no small hurdle, I suppose it depends on the doc(s) - it's taken me 4 months of discussion and a consult with a PhD psychologist for me to clear that my recommendation will be made including an RLE that's non-binary. The reason for the extra diligence is that the insurance requirements document for my insurer is more restrictive than the current WPATH (I think it's based on WPATH 6) and my psychiatrist and I agreed that the i's and t's needed to be carefully dotted and crossed to be avoid problems there.
