If there is to be payroll limits as a price for a salary floor, then I kind of like something similar to the NBA's apron structure. The cap is porous at lower level but the escalating penalties for repeat violators of the top apron makes it nearly prohibitive to stay there. That was essentially the problem for the Celtics maintaining their roster. IT doesn't really penalize financially the guys like Porzingis, Holliday, and Horford who had to be moved. I don't think the NBA player's association thinks it is onerous.