More sports contracts should be set up like this.
The NFL cracked down on some of that back in the 1990s when the 49ers got some very talented players for low salaries and huge bonuses that were very easily achieved. Rickey Jackson was a top free agent linebacker who had been paid more than $1.3 million in his last year with the Saints. He signed with the 49ers the following year for the league minimum (less than $200,000) plus an $800,000 bonus if the team made the playoffs (which they were going to do unless the team plane crashed).
They also made arrangements with corporate sponsors to get the sponsor to sign big endorsement deals with their players to make up the difference between what they were paid by the team and what they could have gotten elsewhere in the NFL.