You keep throwing the word "cheater" around, but you've thus far failed to demonstrate any way in which a player gains an advantage over the competition that they otherwise could not gain by using legal discs. An appropriate term would be "transgressor." Someone who is willfully breaking the rules to use an overweight Halo Destroyer, for example, could simply choose to throw (depending on the exact shape desired or wind encountered) an XCaliber, or a seasoned Stiletto, or a Rive.As should everyone, especially when it involves following rules of competition. You don't follow them, then you are simply a cheater. Some people are ok with that and others are not.
As I said before - if someone is doing something to alter the characteristics of their discs (loading weights into the rim), you're going to be able to hit them on a rules violation without ever breaking out the scale. If they're simply throwing an overweight disc? They're committing a transgression relative to the rules of the game, the person is a "transgressor" but the person is not gaining a material advantage over players seeking out the same shots by throwing discs that are within the regulations stipulated by the PDGA.