I dunno if this has been proposed already but I was thinking last night how interesting it would be if SE used one of their grid-based advancement systems in FFXIV instead of a linear job system, such as was used most recently in FFXII. If you don't know what I mean, your characters growth would basically be charted on a giant graph and as you level up you could move your character in any direction by unlocking new spots on the grid. Every spell and ability and so forth would occupy a certain place on the grid. You could pick a general "archetype" to start (healer, tank, ranged DD, melee DD, support etc.) which would give you a few points set in a certain part of the grid but after that they could leave it up to you. Imagine the customization that could potentially happen. You could in theory have a DD who could heal or buff himself a bit, or a mage with berserk and heavy armor or a tank with reraise and so on. They could even have various spots on the grid where you could unlock "AF" type armors, but you could skip them completely if you wanted.
I know there are potential hurdles to overcome but I think it could work. I'm sure that no matter what SE does for character development this time around, it will be something original for a MMORPG.