I see what you are saying but it would say the best solution currently is making an extension for a path users/me and as method put then I would just make a middleware what sets the ctx.state.user.id to ctx.params.id and then just use as the handler user.update
what does this do the middleware sets the the id in user/:id and then just sends the request to the update controller update uses this would most likely give you the least amount of issues/ maintenance in the long run
I will most likely write a quick plugin later today and push it to github that does this for you. since I think that that is currently the best solution to this problem.
Update talked to derrick and he asked me to implement it in users-permissions