I think grading is worse than P+R, and it will continue the sniping and culture of putting down other clubs down, when one of the few unique selling points that Rugby League has (and the one that has made an indent into mainstream culture) is the "sense of community". If this puts off players and fans from some clubs, and many of those left just hates each other even more that's going to be gone too.
We have a history of kicking clubs out of the top division for "other reasons" (dawn of Super league, licensing, geographical expansion, gradings, etc) and it doesn't do the teams dropping down/kicked out any good. Then later when one of the chosen few fails we have to find a gap to fill and those "unfashionable" clubs have been intentionally weakened.
The grading clearly shows there are more than enough clubs who could make a go of it in Super League than there are places, even if they expand it (which they won't, and in my opinion they shouldn't). Therefore it is unfair to block some clubs from entry on anything other than results on the field.