I dont think your proposal works really and someone else mentioned.
Also are you aware how much work it would be to go back and add elemental properties to each enemy in the game?

From what we currently know CBU3 doesnt want to add more levels so level 100 is the End. thats true.
if they stick with it is diffrent story but currently thats were we are. But while Yoshida didnt say much the new progression seems very much not Item based, they spoke about talents, skill points and ability modifications.
Considering Higher Numbers is what they want to avoid because they dont want a second numbercrush i think Items will have a shallow progression from then.