Yes, especially for MA Mictlan! They should have something that makes them special - and more advanced than EA/LA, too. Probably some sort of cavalry?
As for Eriu - they certainly should get chariots! It's Ireland-based, after all!
MA Arcoscephale... probably cavalry OR some sort of sailing/amphibious unit?
Broken Ermor - the idea of something similar to Nightmares is probably the best... but they shouldn't be called Kataphraktes, Equites with some epithtete would be fine.
Pythium - maybe light cavalry?
Man... don't know. Foot Knight, maybe?
Ulm - they would be best served by getting some more mobile troops. May be even mounted crossbowmen?
Marignon - don't know. An idea of guard of House of Fiery Justice is tempting... but it makes Flagellants obsolete. And what this House would be more in need of is troops with Patrol bonus! Could some be devised?
MA Mictlan - as I've said, maybe some Araukan-based cavalry? Or, say, Crocodile warriors?
Tien Chi - has it all. And Shao-lin monks would be too much...
Machaka - maybe stealthy troops? There were also various leopard cults, etc. Or, if spiders remain the main theme, they could use some quick-climbing troops with siege bonus...
MA Agartha - something like miners? or chakram throwers (these could be missiles best suited for underground combat, actually)?
Abysia - don't know. As they have no close analog... Chariots??
MA Caelum - also don't know. Maybe some other animal besides Mammoth? Say, weaker but faster?
C'tis Miasma - maybe Poor Amphibian troop/mount? Or some non-capital missilers (Boomerang, for example - good range & damage, but few ammo)?
Pangaea Age of Bronze - maybe Centaur Chariot? Or missile-armed Minotaurs (say, javelins)? Or Satir Slingers?
Vanheim - maybe some missile troops besides javeliners? axe throwers?
Jotunheim - Vaetti archers?
Bandar Log - Chariot Archers? Mounted Bandar?
Shinuyama - Kappa with other weapons? Dai Bakemono with paired weapons but lighter armor?
Atlantis - no idea at all.
R'lyeh - human acolyte/cultist in land forts? Maybe warriors of some degenerated tribe?
Oceania - maybe some harpoon throwers?
Eriu - see above: chariots. Plus possibly sacred bulls!