Your real world clone would take 20 years to "make" and be a separate person, like you would be if you grew up when they did.

This is partially missing the point. The goal is to make a separate body, compatible with your biology. There is no need to grow a clone with a functioning brain -- any medical science sufficient to clone a human would be able to clone an acephalic human (WARNING, NSFL, fetus with head damage), and growing a clone with a fully functioning brain (i.e., not driven insane by being grown in a de facto sensory deprivation chamber) would be much more expensive, even if you kept education to a minimum.

Still, all this is ethically questionable, something that would need a lot of advance planning, and will be a long time in the future. It is true that fixing your body piecemeal will almost surely be a better option -- even if it does end up involving some limited form of cloning organs.