Yes, a player can't be forced to stay, which is why this plan would work. There are kids who are high probability to stay, and there are kids who are high probability to leave. Coaches know the difference during recruitment.
Therefore, let the coaches/schools bear the burden of deciding their recruiting strategy. If Alabama wants 85 5*s, then fine. They know they will lose many of them after 3 years. Can they still win with 78 scholarship players one year? I don't know, but let them decide if it was worth it.
Then, during that year, another school has the opportunity to sign those 5*s that would automatically go to Alabama, unless that school deems it too high risk. At some point the recruited talent gets spread thinner across more schools, either by choice of omission or by self-probation. Either way, the field is more level than it is today.