Yeah I tried wrapping my head around possible ways to incorporate black and white magic into the mix, but the way FFXIV is setup it makes it almost impossible to do without making it's own spells and abilities. The problem with that is you might end up with another situation like the whole WAR/PLD debacle where RDM steals WHM or BLMs position in a group, or you make the job so under-powered in comparison nobody will want it.
I thought the easiest way to get around the whole thing was just fit it in a role that isn't being taken at the moment and just have ways to supplement playstyle.