A Semi reaped soul
He is not alive or death , he is both ...
Semi reaped soul, as in reaped by Malthael? Never going to happen. A character needs to be present in the game lore from before the Star fell on Tristram.
As for the concept, I personally think that a WoW Death Knight rip-off is a potential candidate for a future class. Just take a DK and call him Something of Rathma. But please, keep Samurai out of this. If they add Samurai to Sanctuary then I'll be really upset.