The matureness of players skills should rise upon the league level that they are drafting for, but there should be a price for that - their first year salary must be higher, and they cannot be sold, but just fired.
Basically the aim is to allow higher league's teams the abillity to (realy) train players, but not allowing the the advantage of having better assets doing that.
It is already the case now - a team that played more seasons has much higher assets on this game - arena size, players value, etc.
Basicaly there is a problem with the competitiveness due to that, and the draft should not make this issue a bigger one than it is already is (and it is already a crucial issue).