First of all, any proposal that begins with “Let’s pretend the courts won’t overturn this“ is doomed. The only viable solutions begin with what is legally feasible.
Secondly, why would players voluntarily join a union that would force them to give up massive amounts of compensation? With players making upwards of 7 figures, all the higher profile guys will want nothing to do with this. Neither will the schools who have rich donors and boosters.
Finally, all of the unions for other sports usually begin their negotiations around the revenue split from all the money the league is generating. For most of the major US sports that number is around 50%. That is why professional athletes willingly agree to belong to a union. Other than the SEC, none of the other conferences has shown any interest in sharing revenues with the players.