It's not really feasible though:
* Online chess typically uses Glicko ratings (this applies to Lichess and chess.com alike), FIDE ratings are based on Elo
* Online ratings are typically blitz ratings - people tend to play fast games online. Obviously FIDE has blitz ratings too, but over the board chess is mostly standard time control, and that's what's typically referred to as a FIDE rating. A lot of people with standard FIDE rating don't even have a blitz one, because OTB blitz tournaments are arguably rare.
