Suggestions are:
1. Have three different jumping speeds for players. Fast, Average, and Slow. The unathletic players could have very slow jumping animations when blocking shots or going up for dunks and layups. Whereas, the Westbrook's and Isiah Thomas' could have very fast jumping animations. It would make the shot blocking, and inside play alot more realistic. It would also help with layups around the rim. They already do shot release speeds, why not jumping?
2. Have 4 different maximum jumping heights that players can reach. 10 foot, 10 and a half foot, 11 foot, and 12 foot. The top of a players hand should never reach above their maximum jumping heights. This would really open up the game around the rim, and out on the perimeter.
Would this be hard to implement? How would this not make the game significantly better?
The ability to elevate over another person, or get to the rim quicker then another person is a very key element in basketball that is not currently represented in the game.

Comment