I think the best choise is one system of Advance Job / Pestige Class with the chance to unlock the new skill ( G. Katana, 2h-Sword, Raiper, Scythes, etc... ) with varius combination of "base" skill.

For example : DRK → LNC/MRD + THM , now you can use all ability without penalty from LNC/MRD and THM and when you ranking Scythes you unlock unquic skill and traits to improve previus skill

The simply action to rename currenty class with the classic name from the saga, GLD → PLD / MRD → WAR / LNC → DRG, in my opinion it is not a godd idea because you must chance all storyline and skill/ability