Princess does some minor things now. On our last crusie they were talking about sink abrassions. Little wheels which scrubbed the skin away and gave a renewed look.
I would think the crusie line itself wouldn't do facelifts and etc. I think it would be an outside group like Stiener, who runs the spas, that would do the procedures. All they would do is pay for space on the ship. If the medical field could every come up with a way that problems which cause emergencies didn't happen they would start doing procedures in the next few mlonths. But as long as you have a chance of something going wrong with the procedure it will never happen.