should multiple doping athletes be allowed?

Except they're not unimaginable at all. It's happened for ages. Someone comes along with a better way of doing thing;s better training, better equipment, better natural physiology and they go further / higher / faster than others have before.

Look at Paula Radcliffe and her marathon times. Look at Bradley Wiggins and his hour record.

Records will always be broken. But that doesn't by default mean people are cheating.