That's close to a model of running with say sixteen clubs in SL and having auto P & R. This would then largely protect the main SL competition, but keep the bottom four on their toes and give the top four in the Championship a chance to go up. On a CC grand final winner being relegated straight away, another club would get a chance to go up whilst the relegated club recovers. If the promoted grand final club stays up down goes an SL club.
Short term to ensure no yo-yoing I'd agree that model need a Minimum Salary spend in SL, however where to pitch that?? Too low and it won't work, too high and clubs may not be able to afford it??
The over riding question is this this an idea that will be good for the game itself???
Forget self interest??
All other things aside, four up and four down is too much. It creates yo yo ism and/ or threatens mid level teams who don't deserve relegation.
It should be no more than two up two down at the most and I would even be happy with 1 up, 1 down