Think this is a good idea with one addition. That the players if they decide to try professional ball get an opportunity to try out for a team to see how well they do before signing a contract and being declared a Pro. This way they do not kill the college option based on on silly decision.
I think this is necessary for a variety of reasons. For one I do not believe their is a market for too many minor league teams in too many sports so the number of available positions will be very limited. Perhaps just in basketball, hockey and football and the later two would not apply to womens sports.
They would basically be developmental leagues which would require them to be subsidized by the big money making major leagues. I believe that the WNBA barely make enough to pay for themselves so I don't see them being able to subsidize a minor league, Besides they have that in the over seas leagues already.
If we are honest the only sports this might work with would be football and ice hockey. Baseball already has a system in place. Womens sports and other low revenue sports just do not generate enough money to make this happen across the board. In fact if it happened in football it would have a chin reaction that might actually end up eliminating a lot of non revenue sports in college. Why because football generates most of the revenue that pays for the others.
No one one is ever as good as their best game, nor as bad as their worst.