First off, the only ones who are actually preventing these kids from going pro right away are the pro leagues. It isn't the NCAA. The problem is, there is very little incentive for them to change their rules because they basically have a free farm system. And, players come into the pros with a brand, which saves those teams tons in marketing. The reason why the NBA is considering getting rid of the age requirement is that they have a vested interest in the G-League and getting just out of HS superstars will sell tickets (while not using a roster spot if the kid isn't ready).
I'm not on the side of paying players. If they did that, there would have to be some sort of pay restrictions (which would be challenged in court) and they'd also have lawsuits from Olympic sports athletes who work just as hard as FB or MBB players. If you pay players without limits, then Alabama would be paying kids $50k a year on top of tuition.
As far as name and likeness, that I would be fine with as long as it's regulated. What's stopping a booster from paying $5k for an autograph? Or a booster car dealer from giving an athlete a car for doing a commercial? As long as they reported their earnings and the NCAA had the manpower/ability to look into tax returns and investigate income that looked sketchy, maybe it would work. I'd rather have them up the cost of attendance money...even though athletes now have more spending money than the average student.
To me, it mostly comes down to competitive balance. It's bad enough now, if you give the big boys more avenues to cheat, it's only going to get worse. And once fans realize that their teams have an even lesser chance of success, that is going to lead to less eyeballs and less butts in the seats. IMO that is where the NCAA is having an issue.