Sedition difficulty should be near impossible. Never ending Hordes of Poxwalkers trying to eat your face off. Crushers, Maulers, and Ragers like flies on stink. Every mission should start with Mazosi not even landing, just the striketeam jumping out into a sea of death and dismemberment. There should be no rezzing casualties, and if you actually succeed in completing your mission you should be shot by the Commissar for possibly being tainted by the foul corruption of thousands of Chaos infected enemies.
There. No need to make up a new Difficulty level, just make it more 40k-ish. lol
Funny you mentioned that. I said that few weeks ago, that in the 5th character slot I might create a character which I will delete when we fail a mission. Dark(Souls)Tide.