Alternatives for Chaos God LLs and why The Great Unclean One cannot be Rotigus

So there's a lot of talk about the Great Unclean One being Rotigus. The reason it cannot be (in my mind) is because the named GUO in the 8th edition army book isn't Rotigus, it's Ku'gath Plaguefather. The first mention of Rotigus is from 40k in 2018, and then the AoS statline, so there's no reason for CA to use him.

Ku'gath's goal is to breed a contagion that can infect the gods themselves. He also had a ranged special attack that fired Nurglings at his enemies.

I'm actually hoping the Greater Demons are not our LL choices. Early game if they really do live up to their lore abilities, they should be able to rampage through nearly anything early game armies have available to them. I think seeing other names special characters would be more interesting, like Skulltaker for Khorne, either the Blue Scribes or The Changeling for Tzeentch, Epidemus for Nurgle and The Masque for Slaanesh. All of them direct from the 8th ed Daemons of Chaos army book.

Those special characters as LLs means there's opportunities for spending skills on mounts, and other talents. The Greater Demons feel like they should be T5 units for the late game as your faction ascends in power, not grubbing around fighting skavenslaves & Kislev armies of spears & crossbows.