There was already a dude who tried to get into the Olympics with prosthetic legs and was denied.
www.engadget.com/2008/01/17/prosthetic-l...ified-from-olympics/
I think it has always been a risk and reward equation. Does society want athletes who have fantastic accomplishments and then die at the age of 40? The answer has usually been no. But it happens anyway because the rewards far outweigh the risk of being caught and the health risks.
But as you said, if you had the opportunity to be better at your day job with only a slight risk, you would consider it. For most athletes, it's the difference between making a million dollars a year for their entire career, or scoring massive $10 or $20 million salary for the prime of their career. Or between going to the Olympics and winning a gold medal (and a piece of history).
Your point about the term "enhancement" not having objectivity is valid. But if you're running a competition, you come up with a set of rules. And if someone is operating outside of those rules, i.e. by using performance enhancing drugs, then they are cheating. In competition, enhancement does have objectivity. In the academic world, where there are few rules except come up with your own ideas, it's not really as clear cut.