Jones should know how valuable Mcclay really is, particularly Stephen.
If Mcclay is the mastermind, then I suspect they can come up with a compensation that is commensurate with his role.
Equity compensation is a standard way to hold on to key employees using a vesting schedule, and a requirement to sell the equity at market value if he exits will insure Mcclay will not take the equity and work for the Eagles.
I dont know the ownership structure of the Cowboys, and whether it is all Jones.
If there are other investors or owners, then it should be easy for Jerry to swallow.
If not, it may still be easier for Jerry to accept making Mcclay a minority partner than a General Manager (loss of football ego).