What I would like to see, which I think is a good compromise for all (NBA, NBA players assoc., college teams & coaches, and the young players) is something like the following.
1) NBA pays for a 1 week camp for the top 20 HS players, and top 30 college underclassmen.
2) At the end of the camp, each team picks where they think each of the 50 players will go in the draft (Top 5, 6-10, 11-15, 16-20, 21-25, 26-30, 31-40, 41-50, 51-60).
3) Each player will be provided with a summary of this on themselves (i.e. J.Doe you got one 6-10, two 11-15, four 16-20, twelve 21-25, ten 26-30, and one 41-50).
4) Each player will also be ranked based on those scores alone.
5) If you are a HS SR then to apply for the draft you must be in the top 10 HS SRs, or the top 20 (from all 50).
If you are a college FR then to apply for the draft you must be in the top 15 college underclassmen or the top 25 (from all 50)
If you are a college SOPH then to apply for the draft you must be in the top 25 college underclassmen or the top 40 (from all 50
This can be adjusted some if you implement the "0 or 2" rule.