(I want my partner to have a penis - a proper one, that has spontaneous erections and has feeling in it, have always been very swayed by hormones/smell when dating blokes, very clear part of attraction for me). Obviously according to this I must be a massive transphobe.
One of the highlights(?) of Null's recent 4-hour stream about his server troubles, linked over on that thread, was a message passed on by Null from someone who had experienced this first-hand. I don't think I can post the whole thing here, but here's part of it.
I fell for the whole "transwomen are women" line and have actually had sex with a transwoman [...] It is NOTHING like a vagina [...] about as exciting as fingering a very deep belly button.
Oh, and the male body that goes with it still feels male. You never really realize the texture of a woman's skin and the shape of her skeletal frame is so important to the sexual experience, but it really is. There are a thousand different physical cues and sensations that say male, male, male... even with your eyes closed, or maybe ESPECIALLY with your eyes closed.
(Timestamp 1:23:25 for the full gory details).
I mean you can somewhat imagine why someone might prefer, in extremis, to be a simulacrum of the opposite sex, but that's always going to be of limited appeal, because it's only ever going to be a simulacrum, and people are interested in the entire package. You will just end up being neither one thing nor the other.
The fundamental reality is that we don't have the ability to perform sex changes on people, even at an external appearance level. Maybe it could improve, but it's very, very crude at the moment.