They should do the MLB rule. Either go straight to NBA from HS or if you go to college you must stay atleast 2 years if not 3 years. Moses Malone, Shawn Kemp, Lebron James, Kobe Bryant, Kevin Garnett, Jermaine O'Neal, Kevin Durant like talents should be allowed to go straight to the NBA, but Ndudi Ebi or Jonathon Bender's of the world would go to college if they realized its likely they wouldn't go in the first round.
How does this rule actually benefit the NBA? The NBA is making decisions that is best for its league.
Not sure how this rule stops the Bender's and Ebi's. In fact it actually encourages them to leave directly from HS.
Jonathan Bender went 5th in the draft he would still go.
And Ebi also went the first round. His choice at the time may have been - now or go to college one or two year's. If you change the choice - now or wait 3 years, and he is going to go first round... he is certainly going the NBA route.
And now some kids who are thinking one and done or even 2 and done, are all going to go the NBA directly from HS.
As college fans some may prefer this - we ensure continuity, and lose out some one and dones. It's not bad as an NCAA fan.
But it's horrible from the NBA perspective. The main difference is that many players are ready to make a contribution within the NBA within 2 years out of HS -- this is extremely rare in baseball. Athletes are near their peak athletically at a younger age - skill wise and awareness wise the peak is later. This makes a different in terms of when a basketball player and a baseball player can contribute, since baseball is more skill based.
We must also consider that a 19 year old can play the 8-10 role on a basketball team and play 15-20 minutes a game. A young bench player can play and contribute to an NBA team. A young bench player cannot make an MLB team (not enough reps). For this reason, the dynamics that enter the mind for an NBA prospect are totally different thatn the MLB prospect. A HS basketball kid is much more likely to make a bad choice because other kids have had the chance to play that entered.
So for the NBA
1. More Kids will leave earlier that are not ready. They make a decision based on the players that have been able to contribute as 19/20 years old, and anticipate it will work for them.
2. One and Done or Two and Done, makes drafting for NBA teams in the lotto so much easier. Those years in college take some of the mystery out of the process. It totally eliminates some prospects/
3. Kids may enter the draft saying I will only for "X,Y or Z".. otherwise don't draft me.
In conclusion, the "Go Immediately or Stay 3 Year" might be good for the NCAA. But I can't think of one good reason why it is good for the NBA. Why would the NBA want the rule if this is the case?