>>31454939FU and Hell would remove 110 to 120 pokemon from competing with the really trash pokemon.
PU currently has 121 ranked as viable, and 66 of those are in PU already, the other half would theoretically be taken by FU, leaving the lower two tiers with everything on the not viable list. However, the not viable list doesn't include a sizeable number of NFE pokemon that could potentially dominate Hell and Ninth Circle.
Although, considering each tier has roughly 60 pokemon, and there would be ten tiers above Ninth Circle containing roughly 600 pokemon, and that a majority of the remaining pokemon are Little Cup pokemon, I guess I could see things like Delibird being viable there... wait actually, it'll probably die like a bitch to Growlithe or some shit.
I think the problem with trying to create a tier for all FE pokemon is that eventually the really bad ones will just get swamped with LC pokemon that are literally better than them, and then you just have a twisted version of Little Cup.