People just don’t want to watch players who failed at the highest level. The best shot of a league like this working is the G-League after the HS are allowed back in the draft. Bring foreign players around quicker vs stashing in Europe and have a system similar to MLB. Service time doesn’t start until 30 games in a season or something.
But if fans can watch young players who MAY someday help their squad at the highest level, you have a chance. To ask fans to tune in to watch players who couldn’t make it at the highest level is a strategy doomed to fail.