This game isn't built with sub jobs in mind and would probably mean a total rework of every current job to accommodate the ability of sub jobs. If that was the case we'd more than likely get no new job for 5.0, but also a year of fumbling around trying to keep everything balanced in a new system they aren't used to. This game in general is also heavily instanced and with very defining roles so am I just screwed in a dungeon if some idiot wants to sub tank for no reason on his dps. And worst of all PF would more than likely just straight up block u for picking anything but the most optimal. If u want the sub job feel ff11 is still up and running and u can have the ff11 community shoe horn u into the wildly unbalanced end game meta they have, hope u like blue mage or summoner.