I've wondered about a nominal stipend as well, but, this opens a can of worms to. This because ya can't just limit the stipends to players in football, basketball, or women's basketball (the major revenue sports). You're gunna get the crew teams, softball teams, field hockey players and any scholarship student raising hell until they get their $$$$.
The big problems:
1) Title IX (that's all that needs be said, no explanation necessary!)
2) Equity across sports. As an example, what car dealership will bring the women's softball team's catcher down on any Saturday for autographs? But, conversely, is it fair that the starting QB has to share his NIL notoriety with the women's volleyball back-up setter, anyway? But, again, this is already an issue. When the Iowa Women's B-ball team does a West Coast swing with a tournament, etc., flies out, stays in nice hotels, etc., you can bet that doesn't happen if the Men's Football and Basketball teams hog all their money for themselves...
3) Policing: except...one easy solution. No hiring of agents, but simply have the players get a 1099, which gets reported to the IRS. The NCAA may drop the ball a ton on investigating stuff. The IRS, not so much. Still, players can't coordinate all this stuff themselves. But an agent? No, thanks. But some schools aren't a hell of a lot more trustworthy than your average agent. So, how/who/when/where coordinating appearances, autograph signings, etc?
In short, there ae a LOT of things to be ironed out. But, the current system no longer works.