Eh, wrong guy to ask as I love the PA films. Even the lackluster 4th one. The succubus story you mentioned in V/H/S was probably one of the best ones i've seen in a long time but I agree the other segments weren't very good.
That being said, the only idea I have for a Horror themed Found Footage film is a retread on an old idea: Werewolves (especially
Rick Baker looking ones). But I only have ideas for how certain scenes will be played out, no story yet. FF films are hard to write cause you need to have a justification for why the characters need to have the camera at all times and make it all sound authentic.
The Project Exodus script being developed is found footage but more SCI-FI than horror and we made a compelling reason as to why the characters need the cameras at all times. If I ever get that Werewolf idea off the ground, it'd have to be cause I found a really cool exciting way to tell the story.