Hi,
I'm not sure if this has been suggested or not, but how about a Rookie Academy/Youth League along with the draft?
The Youth League can be a development league where you send 16 to 19 year old's to hone their skills.
Once they are 20 years old either they get promoted up to the main team or you can fire them, which would automatically send them to the Transfer Market.
Each Youth League Team carries 12 players on it. Training can be a little different in the Youth League by having INDIVIDUAL skill training for players as a option so that they improve on a fundamental skill like REBOUNDING or DRIVING for example.
SPAZX