I don't think in season NIL needs to be connected to play or even should be connected to play in most cases. For example, here we might be talking about a player playing at a representative value higher than he signed for. Now it does make sense he may want or ask for more and to many it may seem like he should get more. But what about a player who underperformed per his original representative value? Should that similarly mean a school or collective be able to take money back from what was originally offered?
I think formal contracts ahead of the season clearly are the way to go. You meet the expectations set in the contract that you agree to, and you get the payment the school or collective agrees to. The real question is how do you get some semblance of continuity from season to season without everyone looking for the next best deal. And I've talked about this before but I think it's used the idea of longer term contracts with "vested" income that is higher than single year income that also offers things like insurance, health care, and financial advisors.
For example:
Program A has an intermediary offer you $250,000 for 1 year cash.
Program B offers you a formal legal contract of $450,000 over 2 years with $150,000 and benefits guaranteed and the full $450,000 and bennies if the player stays for the full 2 years.
Basically it makes the player choose whether they want to go the riskier route of year to year shopping that Program A offers but could potentially provide a higher overall payday if everything goes right, or to go with the more conservative but stable approach of Program B that insures against possible loss of income while not having the same profitability ceiling.
And while there's obvious risk for longer term contracts for schools as well, setting up long-term contracts like this may insulate you from bad years with appropriate money management