How many rounds each year in the draft for that other league?
We could always include an age in the mandatory promotion to weed out some of that, or cap the minors at 20 with the reduced prospect draft rounds just to prevent someone from going nuts. The idea is obviously to increase flexibility, not insanity. As I said, I don't know if it would work or not, but I think it's an interesting discussion to have.
* Agree with Dinger, 500 owned prospects is crazy. ~240 ish like we currently have makes sense, it would just be nice to be able to have more flexible distributions of them.