Also, someone could get into legal trouble for forging the signature on a contract. If the player's lawyer oversaw and approved such a forgery, he might get disbarred.

I have have seen old time contracts were someone official signed for someone else (ala the Yankees VP signing for the Yankees President, the Presidents listed on the contract). But in such a case, the signing VP added his name and position below and clearly noted that he was signing in official capacity for the missing President. The added line made sure there would be no confusion then or now.