TP mattered in XI and 1.23, ARR not so much. I'm not sure theres any hurry in changing it but.. Maybe they could re-work the tp system as like a pseudo xi tp build up system? AA build small tp, weaponskills build more tp, combos having a tp build bonus. Then TP consuming finishers that can only be used once you have enough tp and consume all tp. You would be doing the exact same thing you do now just with some instant weaponskills/abilities that you would throw in to consume your built up tp (maybe even the 100-300% bonus if done right). If balancing mages against that was too difficult i don't see any reason other than tradition for why mages can't gain tp from spellcasting.