Would rather the complete dissolution of the class/job system and just make them all into full Jobs, don't even have to unpair the experience, Take archer at 30 the archer class becomes Ranger, and splits from bard as 2 full powered jobs that don't share certain characteristics. Ranger could even become a Limited job so they don't have to balance it for major content and it can be overpowered for fun and enjoyment. Same with Rogue, at 30 it becomes thief, and splits from ninja, also limited and unbalanced. Pugilist = Boxer/Monk, whatever the base class becomes is a limited job strictly for fun and creates a whole new unbalanced and fun division of the game while still leveling alongside the parallel job. For instance at 30 Thaumaturge becomes limited job Sorcerer and regains the full elemental wheel, White mage splits from cleric and cleric becomes Exorcist with a full battery of uncontrolled light aspect magic to burn, Arcanist becomes limited job Elementalist and summons greater summons and elementals.
SE could have so much fun with this idea with Limited jobs allowing them to take off the kid gloves and make these new class jobs redonculously overpowered, but fundamentally separate from traditional group content. Eventually it would be possible for SE to implement the kind of batshit insane hard content they've always wanted to but with the Limited jobs taking point and focus in that content. So you'd have the safe traditional game with balanced content and cooperative groups then the insanely hard and fun content with the unbalanced limited job system in play exclusively.
My list: Main / Limited
Lancer = Dragoon / Judge
Thaumaturge = Blackmage / Sorcerer
Arcanist = Scholar:Summoner / Elementalist
Cleric = Whitemage / Excorcist
Pugilist = Monk / Boxer
Rogue = Ninja / Thief
Archer = Bard / Ranger
Gladiator = Paladin / Champion
Marauder = Warrior / Berserker