1.gothmogtheorc is currently planning a Last alliance mod adding in all the last alliance units to the game, he's also working on a minas morgul faction mod.
2. I don't think taht would be too hard, except for teh animation part
3. i beleive taht would require some modelling etc. not gothmog's forte. sorry man, but you've said it yourself
4. Gothmog exists in several mods already, and I know he may be included in Celeglins Elven Alliance
5. been done, check around. especially on the tutorial part of this site, adding nazgul is easy as pie. just add the extra entries in mordor's playertemplate.ini
6. khamul is not meant to be a ownage hero, simply there to fill the leadership gap for the rhun soldiers, and to be a representative of the easterlings
7. check out Vaps mods, he has a sauron... many mods have sauron...
ps, as far as I know gothmog is working on several mods as it is, large and small. and most of what you suggested already exist in several mods.