Might make sense for it to be Menzies. Since Balthazar ended up being a megalomaniac that wanted revenge above all else, it might make sense to recontextualize Menzies as "not as bad as we thought." Maybe all the stories about him were just really bad press from Balthazar's propaganda machine?
Then again, it would be cool for him to have a "gray" vibe similar to Jormag. He became a new god out of need for a quick replacement, so the other gods reluctantly chose him with no better immediate options. He is being kept in line by them, but he's still pretty shady. Might make a good "frenemy."