A) The Levellers do not all use undead. In fact, none of the Levellers use the same thing. Balor used undead, but your gonna have to think (and model) something new for Alric. Prehaps you can explain the origin of mahir while your at it.
B) Dont forget to resurrect some of the nine to be servants of Alric, just cause we love them so much, and remember that he has a sh*tload of artifacts including the Ibis Crown, a Tain Shard, and the Elbis Stones.
C) The Ancient Evils should return once again, after all they are Ancient Evils. Or have they been permenantly destroyed?
D) Your also gonna have to completely redo many of the Light's forces. After all, a millinea has passed.
E) Heres my tip for your Alric from the sea idea. When Alric died, a great ceremony was held and he was placed in a burning ship sailing towards the west (much like the ancient vikings did) with his artifacts and sword. Hundreds of years later, The Leveler (Alric, but we dont know that do we?) returns in a huge, black iron war galley accompanied by an armada manned of a forieghn race technologically superior to the Myth World. Prehaps they can use Golems (clay, iron, water etc), maybe even Zepelins or Gliders or something.
F) I'd have to agree with the theory that the Ghols would be on the side of the light. After all, Balor hated the Myrkridia, Alric the Leveler would prolly hate ghols right? Maybe some of the former light units would be on his side though, prehaps Bezerks or Dwarfs could be bad.
The Bottom Line is THIS PROJECT IS AMBITIOUS. Its probably nearly impossible. You have to do the scripting and writing of creation, and the modeling of Jinn. So your in no danger of it being released before Chrimea hehe.