Why not use the Championship as a development vehicle for this???
For me - I want loans between Prem academies and the Champ, with a proper competition between the two.
In my ideal world, I'd clarify the PRC as a development competition (just "no first XV players" for the Prem teams - or "no-one from your European squad" 15/23 to be U25... something along those lines) and expand it.
I'm not sure I've got details worked out in my head; but with the Champ clubs not having the distractions of European rugby to worry about, there should be something workable.
I'm thinking of a calendar where the Champ clubs play against Prem clubs during the international windows (including training weekends?) - with the loan players playing for their Champ club. Whilst they play Prem v Prem and Champ v Champ between the AIs and 6N (probably loan players playing for Prem club).
This way gives the Champ clubs competitive matches against Prem clubs, and hopefully fewer walk-overs, whilst getting the academy players game time with both their teams; keeping a longer season for their development. Also gives the Champ clubs more matches (and gates) in a year, hopefully more attractive for TV companies, and more variety for fans.
I'd rather that than a full-on A-league that's yet another "up yours" to the Champ, and yet another ring in the fence.
Details obviously need to be worked out. It would also need some funding before TV deals are worked out and popularity assessed. Making it least likely though, is that it would need cooperation and a degree of selflessness from PRL, showing a desire to grow the pie rather than fight off all attempts to reduce their share of it.