So three major things:

1) Elements have been relevant in FFXIV since, well....never. A vestigial system leftover from its ancestor game. Unless there is anything that distinguishes those elemental attacks other than element (i.e. one having a dot, one being an aoe), then the element theme is pretty much pointless from a mechanical standpoint. Even the elemental vulnerability trick seems pointless when we have a skills that create vulnerabilities for ALL elements in the forms of Foe Requiem and the Promoted Bishop Turret.

2) If they can only control the elements around them, wouldn't that only make them a geokinetic? Wouldn't it make more sense for a geomancer to be able to create the environment of their choosing rather than being forced to the environment they're stuck in?

3) I'm still not really seeing the support factor as much compared to summoner (eye for an eye, resurrection) and if it's supposed to do less damage than summoner or black mage on single-target, then it doesn't seem like there's any point in bringing them to most endgame content. It would need something to make it viable for those circumstances, whether it be more single-target damage or more raid utility.

I do like the idea, but unfortunately it seems more like a testament to how unreasonable it is to expect certain ideas from FFXI to work in FFXIV. Keep working on it though; we need more casters.