Also masturbation might be a challenge in that scenario.

Also the ability of mirror neurons to watch someone do a thing, then conceptualize and execute it with your body is extremely interesting.

Agreed, until prosthetics can achieve full parity of both function and sensation then they are only good as replacements for parts that are already missing. No sane person is swapping their hand for one that lacks a sense of touch just as good or better than what they have already, even if it's mechanically superior. In such a scenario that mechanical superiority is desired they would opt for an augmentation over a prosthetic.

I think with the beginning stages of this kind of technology would work better with a removable option, for this reason. We are already getting able to make better human appendages, with super strength and dexterity, etc., but the touch is something that will probably be hard to implement for awhile.

i feel like being objectively better than your body is a pretty fundamental requirement for transhumanism, like generally what's shown as the ideal transhumanist body is a nanomachine swarm that can just make precisely whatever you want at any moment, you can be ostensibly human one moment and then turn into a fucking jet plane and go to the other side of the world and become human again to traipse through the jungles.