FYI, in all jurisdictions I know of, this is already the case. I.e., a non-compete period in which you are not paid to a level commensurate to what you got before is not enforceable. If employers try to enforce them in court, they will lose.

Source: had a non-compete clause in employment contract that had no mention of any pay during period. Employer initially did not want to pay me anything during period. Hired some lawyers and they paid 100% of my salary during that period. All the lawyers did was write some letters, never had to go to court.