If it's up to me, if some sort of item level has to stay, I would just stick with level equip requirement plus grading it by 1s with high quality items going up 1 grade above the nq.

So gear with lvl 50 requirement will be 50.1, 50.2, 50.3..Then when the level cap to 60, it'll be 60.1, 60.2, 60.3, with maybe late 50 gear (rating 9 or above or something) easily trumping lvl 60 gear with rating 1-3 easily.

The content entry requirement would be based on adding them all up together as long as they're the same gear equip level. Someone with all lvl 50 grade 1 equipment would be somewhere around 12-13 points I think?