Looking at the way this game was being set up earlier it seems that they had the groundwork for each class/job to be able to perform two types of tasks in battle.
They had things like Bio and Dia. Party buffer that gives spikes that give you back MP when hit.
They do not want to add a support role to this game, that is fine. Then let certain jobs have a side of them that lets them support the party to an extent. This game thrives so much on doing DPS so fast but lacks a lot of the defensive abilities. If we had ways to place debuffs on monsters (includes bosses..) as well as being able to enhance our party's survival somehow..it would help a bit.
I support the two ways a job could play. PLD's could get a their sword oath boosted and attacks enhanced while in that mode. They also are about protecting, so giving a party wide AoE defensive boost while off tanking could go a long way.