Yes, the Clerics both good, evil, and neutral would all be good...however, they should only have limited power...so if a unit of 120 has sustained 60 casualties or 50% than the Cleric could only heal 1/2 of the casualties so they would regain only 30 casualties and be back to a strength of 90, Each Cleric could only do this maybe once or twice, and if a unit is destroyed than there is no way that unit could be rehealed. Unless there is a way I could implement necromancers

Also mages or war wizards would be good thing as well, but mostly faction exclusive...being the Dragon Empire, Knights of Solamnia(auxiliary mages), Silvanesti, and Qualinesti. And now that the .CAS file has been found and hacked, Skinning shouldn't be a real problem. The Humanoid races will be easy to do as I have already found a believable elf model for 3dsmax which I can convert to fit in the RTW engine.
Magic will be a difficult thing to implement, besides Dragons, this will be my second biggest concern. I think that Fireball will be easy, but I also want Sleep Spell, Freezing Spells, Electric Spells, Illusional spells...a truly horrorific endeavor but if I find out how(and I am working on it) then it would be truly great. BTW I got approval from RTS to do this game.