I'm new to this year's game, but not the series, but if you don't go with the whole re-rating suggestion, my suggestion would be to find the guy you find most similar in the default rosters and make his ratings similar, and tweak them to your liking or what you perceive is the reality.
Like for Hogan I basically did Cena, increased/decreased certain specific attributes and went from there he came out 93 rated. If you do it this way at least the ratings will pretty much be in-line with other wrestlers in the game.