Isn't that basically what starstorm is?
In the Titan 16-bit parody they even use the comet animation for the lv2 caster LB.

I think we need to be a bit more grounded in expectations, there were more "ultimate" level spells than ultima they can pull from such as tornado, break and freeze.
Or these would be good examples except they kind of already have set roles and classes, two of which would go to WHM if they implemented the spells for player use, and the last, freeze, which already exists and is utterly useless....
I think I can see why they created the new spell Foul now rather than using an existing spell.