I always wondered why there was never another game based on the Planescape setting, not even close as far as I know. It allowed for such a broader range of potential, weird characters, and fantastic situations than the traditional 'elves, dwarves, mages and humans-with-swords' fantasy setting.
I realize PE isn't going to be in this setting, but any chance of adding a dash of it to the game? Maybe an NPC who is a Modron or some berk from Sigil, or even a quick side quest to one of the planes? There are such colorful and trippy possibilities.