I don't think the unit size limit is too bad, but I have never played Faerun with Ermor in a leading position... It is mostly a question of playstyle IMO, however, technical things shouldn't limit those.
re
tion replacement mod
Unfortunately, I couldn't make that. No special effects of dominion, or any nation-spesific special qualities, can be changed. This includes undead spawning, ability or requirent for Blood Sacrifice, halved temple/lab prices, Constriction, spawning of R'lyeh freaks, etc. Starting summons and heat preference can be changed, but other than that, most abilities can't be modded.
In Dominions III most of these abilities become moddable.