You shouldn't get to say what another person does with his or her body. It affects no one but themselves and the doctor they are paying. Plastic surgery shouldn't be limited to certain people for certain reasons. Just because you think some reasons are better than others doesn't mean you (or some other governing body) get to tell people what they can and can't do with their own bodies.
There are many, many people each year that undergo plastic surgery for purely cosmetic reasons that don't end up looking like Valeria Lukyanova. I believe that if you start to show a propensity for being addicted to having plastic surgery then they should require a psych appointment before future surgeries. But for the typical nose job, no, it should be allowed.
The problem with capitalism is it puts money in people's hands who simply do not deserve it. People like Valerie Lukyanova who get plastic surgery, over and over again, don't deserve the wealth that they have. The money could be spent in far better ways, but that doesn't mean some governing power should stop her (or anyone else) from getting plastic surgery just for vanities sake.
The human body is not designed to be perfect, but it is designed to be functional. Plastic surgery is part of the downfall of humanity. Originally it was designed to help people who were burned or injured. But humans found a way to make money off the sufferings of those who feel they are not ''good enough.
No, plastic surgery should not be allowed, if it is only for vanity, because people can do themselves considerable harm by getting plastic surgery just to look more like Barbie. If a person has a mole or wart that makes them self-conscious that is different. But just to look different than you are is no reason to go under the knife.