Mictlan

[Nerfix]

How about adding some of the features the summoned units are called for the national units?

Light infantries could have some terrain survival traits and elite units could have minor resistance to elements or magic, and some of the units could have magic weapons. Say, a Knight of the Chalice might have a magic sword that has an AoE 1 attack that damages undead and demons as an addition, and 25% fire resistance.

Maybe all sacred 'knightly' units could have weapons that do anti-undead/demon damage. A KotC or Black Templar could take on a Devil and actually whoop it's barb-tailed rear.

Temple Guards, who are admitedly good now, could have a 25% shock resistance slightly stronger weapons than regular caelian weapons.

Same goes for other nations. Saber Cherry (IIRC) had a mod which gave the heavier Ulmish unit a 25% Fire/Shock/Cold resistance and slightly improved MR along with other tweaks. If I remember correctly their weapons were also considered magical which propably helped a lot against ethereal units.

And so on. These are just some minor suggestions, and shouldn't be by any mean restricted to just the nations I mentioned.