Be interesting indeed, as much as people complained about XIII people tended to like the La'cie and all the focus thing which I think was the coolest part about it, you do this or you turn into a horrible rock zombie.

I think some elements would work while others won't. The world of XIII, type 0 and XV are all a modern setting but that could work if the Garleans was that Modern setting, so like they were the La'cie or a chosen few, and they still had a emperor but he gets his power from the Fal'cie.