So this is the least likely DLC idea that still makes some sense to me and still in theory seems possible with what we know, and I came up with this...monstrosity.
Count Noctilis is attempting to control The Galleon's Graveyard, and dumps in a bunch of magic to try to do this. He realises that in order to do this properly he needs to carry out the ritual at both ends at the same time. He realises that the other end is the great Maw in the Mountains of Mourn, and he sends Skretch Half-Dead around to co-ordinate the ritual, and take control of the Maw once and for all!
The Ogres realise that something is going on, as they see that the Maw is getting a bunch of magic from some nefarious source. The butchers use the power provided to the maw to ressurect the first Ogre Butcher, Groth One-Finger, to defend the Maw against any who would attempt to turn it against them, not realising that he might turn against them himself...
Skretch Half-Dead would be a Legendary Skaven Vampire Admiral, and would maybe come with a generic version of himself as a generic lord. He would have access to a hybrid lore of some sort; Ruin with either Deeps or Vampires. Most importantly however he would be able to access underway stance, critical for navigating the Mountains of Mourn, which is both the in-game and in-lore justification for why he's the lord that is sent across the world. He would start right in the north of Ind/south-east of Darklands, near the Haunted Forest. For a faction mechanic I was thinking something like Repanse's water mechanic, where he can see underwater rivers that strengthen his forces (coupled with a general Vampire coast buff near water and nerf inland); he could maybe also have a sort of Ikit/Throt lab style mechanic for his vampiric troops. He would have a couple of undead Skaven units, and also a couple of undead Ogres and maybe a couple of other races.
Groth is just another Butcher character I found (I'm not going to pretend I know a massive amount of lore, especially for the Ogres), but I think could be interesting if they lean into the whole "ressurected" character, maybe even making him Ethereal. His people are also particularly savage for Ogres, so he would have access to outright cannibalistic (and reveling in it) Ogre units (probably only him, think Eltharion's Mistwalkers), and so his campaign would be a bit like Tyrion's "Bloodline of Aenerion vs Defender or Ulthuan", where he can either go all-in as a defender of Ogre-kind or all-in as serving the Great Maw to the expense of everyone, including the Ogres! For the DLC units I don't know, whatever isn't done in the main Ogre Kingdoms pack that there's a vague lore justification for.
Gameplay wise this would play somewhat like the Twisted and the Twilight, or even the original Vortex campaign. Skretch would have to take and hold a certain settlement next to or on the Great Maw itself before a timer expires (like Eltharion or Throt he would be able to trigger the end battle(s) before the timer runs out). Groth would have to eliminate Skretch's faction while holding both Skretch's starting province and the Maw for a few turns. Both factions would have to win two seperate battles at the end within a couple of turns of each other- one with/against Skragg the Slaughterer at the Great Maw, and the other with/against Count Noctilis at the Galleon's graveyard. I would also introduce a midgame "skirmish" battle where you can fight at the Maw for a first attempt at the ritual - the twist being that this battle is unwinnable for either faction. The aim then becomes to take some key macguffin to control the Maw, before retreating (again like Throt's battle). For Groth at least depending on which "choice" he makes he either has to defeat an Ogre force or some kind of "Great Maw" regurgitated army at the end of the final battle.
So yeah, this is never going to happen of course, but I had fun imagining this up. If CA are stuck for ideas in 6 years with the Warhammer III DLC sales still rolling in then maybe they can take some inspiration here!