For me the problem is how they'd look as 1/6th figures. Personally, the appeal of the scale and nature of these figures is getting the realistic sculpts of the actors and the soft goods. Raziel is a walking corpse who'd need a special body and essentially he'd be an all-plastic figure. Kain would fare better, but he'd have to either look like an oversized action figure with joints all over and whatnot, or go with one of those seamless body which risk cracking. And then there's the pleather.
A part of me would love them, another thinks it'd be useless to want them in such a format. My "solution" is to hope MCU Dracula has the Curse Of The Mutants redesign, since he's similar to Kain. It wouldn't surprise me if they were inspired by Kain, who in turn always seemed like a mix of Stoker Dracula and Elric Of Melnibone to me, bringing the thing full circle.
Still, I think that even if LoK figures were to happen, I wouldn't be able to put them next to an InArt Joker, you know? Not that I'd put them there, but you get the point. They'd be too toyetic and fragile. Maybe if a reboot/continuation happens and they make everything a bit more realistic and stylized to gain a new audience, so that their designs would lead themselves better to this scale.