Color me skeptical that more than half of D1 football players are going to want to unionize.
Right now, being a power 2 starter in the transfer portal is gonna get you easy six figures, even if you're only decent. These guys are not going to continue to make this kind of money when/if this all sorts itself out at a healthy equilibrium.
Players will want to unionize because it's massively beneficial to the bottom 90% of players to do so. It's the same reason why LeBron James and Patrick Mahomes, even though they could command a lot higher % of the team salary cap, are part of the union and don't complain about it. Furthermore, Unionizing allows them to not only negotiate money, but healthcare, eligibility, minimum standards for practice and player safety, everything that goes into the sport.
Assuming that the players union doesn't negotiate by seniority, a rough estimate for the per player salary would be something like:
50% Revenue Split = $55 million (Big Ten teams are collecting roughly $110 million, perhaps more, in football related revenue)
105 Players sharing $55 million = $524k per player, per year. Obviously, the structure may change where a 4th year player gets more money than the first year player.
This kind of money is much higher than the vast majority of NIL payments 90% of the roster is collecting, and I suspect even the massive NIL contracts we hear about are numbers that equate to the entire contract and not the per year numbers. But even outside of that, NIL payments are going to end up uncapped - it won't be legal to limit how much an athlete can make off the field.
I also don't think that non-Football athletes will be collecting that much of the money. if Title IX becomes an issue, schools will legally separate the football programs from the University to get around it - which very well could invite Congress to get involved.