Nezarec's Sin already does that for Void builds, along with Contraverse Hold and to some extent Briarbinds. Verity's Brow may be for most Warlock subclasses but it can excel on Voidwalker. I wouldn't want to see yet another ability regeneration exotic.

Out off all of those options u listed only two are void specific, contraverse holds gives nade spam,Briarbonds enchanting class ability spam. I listed those options for skull because I actually have a gm build with it that I like and those would be what I would like for the exotic. I also am perfectly fine with more ability exotics, honestly if we wanna keep things simple here we could simply have it give you small chunks of super energy for every kill while devour is active.