So I'm admittedly curious, what is the win-con? I can see Champion getting relatively big and Vexing Devil causing a few problems, but I don't really see where you're getting far beyond that.
Since you're looking to play with Immortal Servitude and already have red and black in the deck, why not toss in 4x Blood Artist and 4x Rolling Temblor. The idea here is then to drop the Blood Artists, wipe the field, land the life gain/drain from the creatures dying, and then reanimate all of them with the servitude to repeat. Given that the artists are at a two-drop, then you have the ability to toss in all sorts of other two drops - most of which are more dangerous on their own than many of your one drops combined (I'm thinking Ash Zealot, Strangleroot Geist, Flinthoof Boar, Elite Inquisitor, etc etc).
Anyway, it seems like a neat deck idea, although I'm not sure it will prove all that viable in a competitive setting; but definitely fun for the kitchen table.