This is kind of just a thought experiment, obviously it will not affect any change. I just think it's an interesting concept.
There is no incentive for a pro league to abide by a draft grade. Obviously, this is to the harm of the athlete that is given a high draft grade, then drafted low or not even drafted at all. So here is the solution I will pose:
The NCAA should allow student athletes to opt out of a draft if they are drafted below the round that they're provided in their draft entry evaluation. Obviously this harms the pro leagues, so I know the NCAA would be hesitant to enact this. However, if they want to pose themselves as an entity that helps student athletes, it seems like a no brainer. I think they want to use the specter of ineligibility as leverage against athletes leaving, but it really does harm more than good..
If ineligibility is not a threat, more kids would seek a draft grade. That would put an incentive on the pro league to honestly provide, or possibly lowball their draft grades, so that kids are required to go pro if they declare. It forces the leagues to put their money where their mouths are. Kids will get an honest barometer of the worst case scenario as the leagues protect their interests in assuring that kids that declare are drafted.
You could have two options - either make it so that if a kid is not drafted by the end of the round promised, they are off the board completely. Or, alternatively, you could allow a team to draft them and take the risk of having the kid opt out.
This makes a lot of sense, which to me means the NCAA will in no way entertain it. More of a 'king for the day' type idea.