I think all chapter masters should be lords of war, at least of the original legions. Think of the power they have at their command. Mega buffs or straight up combat monster. Abaddon should be too, he seems woefully underpowered on the table top compared to what I've read in the books. I'd agree with the Sanguinor and the Avatar. All the really big tyranid ones should be to, in my mind.