The explicit connection between

a school's apparel provider hiring players for endorsements placed into a school's contract with the provider could still be prohibited.

Frankly, the better solution to prevent the problems you're discussing would be to prohibit requirements that the athletes wear specific apparel other than that needed for purposes of team identification (e.g., shoes would be up to the player).

Players could then freely negotiate with companies for those items, regardless of the contract the providers have with the schools. This would be a good thing, as it would properly split the value that the school's brand is providing the apparel company versus the value the individual player is providing.