The game already has this. You can level your character to 60 and cap. but you can still progress because of the second leveling system - ilvl.

Increasing ilvl increases your attributes via the gear itself. So you progress your character overall first by leveling the job and second by leveling the gear. Each new patch advances things further.

Going back to ARR when the game landed you could get to level 50 and ilvl 90, by the end of the patch series itwas ilvl 130/135 if I remember correctly. Doesn't this really accomplish the thing you are after without adding to the skill bloat?