I agree that a developmental league would be beneficial.
I’ll go a step further in that I think a number of teams have bad head coaches that don’t employ coaches who are good at developing players. Some teams seem a lot better than others are developing young players.

I look at the Jets under Rex Ryan. How many young players did they develop? Mohammed Wilkerson was a #1 pick, and clearly talented. What about lower drafted players? In 6 years I can think of only 2 who improved: Matt Slauson and Damon Harrison. Rex cyt Danny Woodhead, and Belichick snatched him and he became productive. Bilal Power has been good the last couple of years, and thats after Rex was gone. Maybe he improved own his own.

A developmental league would give players an extra chance to improve. The problem is the injury risk. But it’s worth the risk if you are dealing with fringe players, who might otherwise wash out.