The RFU is the governing body, they hold the players registration, can sanction clubs or players who break ranks & also own the only profitable item in rugby in the country, the England teams.
To break away from the RFU would be a massive undertaking for any club or organisation that wanted to attempt it. The only similar thing I cna think of in organised sport is Kerry Packers World series Cup, where a TV station signed up the cream of international crickters to play in a seioes of matches played under, at teh time, innovative rules & conditions. Although that didn't last, it did force cricket into the 20th century, it did ultimately fail with the national cricket boards regaing control.
Although rugby has some problems, its at a very different point to where cricket was in the 1970s. There are endless ideas & variations being thrown around, its more about choosing which path to follow rather than trying to think up new ideas.
IMO, I think PRL will wait till the end of the season to see if any other clubs go under. Once that's decided they can end the relegation debate as all P share holders will be in the prem (they could invite Ealing in if they wanted to round the numbers up) and none of the clubs will argue. The RFU will be probably have to accept it as their chief asset, the England team, will depend entirely on players in the prem. The Champ clubs will be left to decide if they can afford to be fully professional teams, I suspect many already arent anyway!
Like I said early, a really bad time for Warriors & Wasps to be without their P shares!!