An epic/legendary skin for Gul’dan, from an alternate reality where Draenor was conquered by the Naaru’s Holy Crusade, using Gul’dan as their prophet.
I sadly have no artistic abilities to draw a concept, but I imagine Gul’dan looking something like a WoW priest, with the golden light markings of the Lightforged Draenei. Maybe a shorter, more well-kempt beard than his warlock counterpart, to make him seem healthier and more youthful, as if I remember my lore right, he’s actually a lot younger than he appear.
Abilities would take on holy light based animations, and he would have custom voicelines of a fanatic zealot, maybe some interactions with Whitemane (agreeable) and Uther (animosity).