I feel that currently FFXIV suffers from an issue that is only going to get worse in the future. And that is the issue of making an interface usable on both keyboard/mouse and controller. To help mitigate this issue as much as possible, I feel the dev team should look at implementing parts of it in different ways.
AOE Toggle right now is an inconvenience, and it consumes an entire button on the controller. This button could be used for many more important things like cycling through target modes, or toggle battle regimens. With the redesigning of the combat classes/jobs/roles/specializations/whateverpeoplewanttocallthem, I think that would be a good time for something like this.
I propose the AOE toggle gets removed to free up the button on the controller for more important functions, and in place give us aoe -ga spells. This would give classes a bigger variety of spells, and possibly make some classes unique. If Conjurer had aoe -ga spells but Thaumaturge didn't, that would be a really great thing to seperate the two classes. In addition, this could open up possibilities for new jobs on the future. You could make certain jobs specialize in AOE effects and others in single target effects.
Think about the current Archer debate found in the General Discussion forum right now. By making some classes specialize in AOE and others in single target, you could do things like make Archer/Lancer aoe specialists (Archer having various volley attacks, Lancer having sweeping attacks) while Marauder and Pugilist would be single target specialists.
I think that by removing the AOE toggle, it would really balance out some classes and present some excellent opportunities for class uniqueness. Just think of how important Scholar was in FFXI. The ability to AOE any spell they wanted to was huge, that was an entire role in itself. FFXIV gives this ability to every class and sort of homogenizes them.