FF Tactics job system as far as i'm concerned, combined with something else to acquire abilities. Something like the guild marks (getting them like before, unlocking depending on job/class rk and corresponding quest done, was a fine system imho) (blue will get something like IX/XI, but needs a one-use "capture" ability that can be bought with gms ) + Physical level (allow a nice level of originality/specialisation of your char).

Call me nuts for loving those old systems, but they were the main selling point in my case.

Materia as it is now, with special combinations