Wish i could help with the model work (that Badb is looking sick!) but alas programming is my forte, not modelling or rigging.
The new unique features look very nice, though i wonder what sort of madman would willingly enter the Tapesty House Entrance / Kanna's Gate. Foolhardy adventurers, i suppose.
Is the grenadier file the same used by the recently implemented grenadiers? It is odd that it would give an error since it already exists in game, though saying that i haven't actually seen them in use (but i guess they would work since they look like standard Civ units).
Vanilla FfH uses <KFM>Art/Units/Grenadier/Grenadier.kfm</KFM> for 5 units, and other Grenadier.kfm files found within specific unit folders for 10 more units. (Most of the customized ones are for arcane units that I presume include special effects to show magical attacks.)
MagisterModmod uses a Grenadier.kfm for two dozen units, including the implemented grenadiers (which just use vanilla Civ4 art from the original model used as the basis for all the others.)
I was frankly surprised that Grenadier.kfm worked as well as it did, given that it is trying to animate a mounted unit as an infantry unit. The other kfm files I tried either caused the unit to be completely static or hovering while bowlegged.
Yeah, while the Devil Portal art is nice I wasn't sure either if it is the best representation for an entry to the Tapestry House. It is part of hell, but should be more seductive than foreboding. I just came to dislike my Mercurian Gate based artwork more.
I've been trying to see if I could find any building or improvement art that is compatible with the Succubus art, and finally found one of each: the Orbis Mod's building for the Weavers
Tapestry Guild and the Snake Pillar.
Attached is a possible candidate which combines that building, the snake pillar serpent, and a dozen Succubi.
If I go with this version I'd probably call it "Kanna's Foyer" instead.
Edit: i just uploaded an image of an updated Kanna's Foyer, with some Succubi moved/resized and the color scheme made more appropriate for Dimensional Mana.