Ideal civs...hmmm...an interesting issue. There are lots of ways to go, and all of them have appeal/flaws. I guess I'll take a page out of the Civ3 manual and mix ancient civs and "modern" civs and come up with a list like:
Hobbits (Shire)*
Noldorans (High Elves) [encompass houses of Feanor, Fingon, and Fingolfin]*^
Sindarins (Wood Elves)*^
Dwarves*^
Mordor*
Morgoths' Realm [does it have a good single name? I can't come up with one]^
Easterlings (Rhun)*
Southrons (Haradrim)*
Rohan*
Gondor*
Isengard*
Arnor*
Edain^
Numenor
That list is both too short and too long. I would really like a second dwarf civilization, but they never really existed in great numbers and I'm struggling to differentiate them other than by home "cities". Moria, Iron Mountain, Lonely Mountain...but those are more just areas than different "strains", in my mind. I should probably reread the death of Thrain again and the dwarves revenge...maybe that would have some good notions for me.
I also want to include a "forces of nature" civ, or something like that, for Tom Bombadil/the Old Forest/Old Man Willow, the Ents, Caradhras...maybe even Dead Marshes. Never let them build settlers, though (or something like that).
The 11 marked with *s would be my "scenario" vision of the War of the Rings. I only have 5 marked with ^s for a First Age Siege of Angband scenario, though, which is too few, in some respects. But I don't really want to mess with the various Noldor houses and what to do with them in the Third Age. Sigh. It's very difficult.
I would also like to remember the humans that fought on Melkor's side. Maybe split Edain into "House of Beor", "House of Hador", and "House of Haleth", but that still doesn't list the evil people. It's been too long (almost a year now) since I've read the Silmarillion.
And, in actuality, I'm mentally including all the Moriquendi in the "Sindarin Elves" category, even though the Avari and Nandor fit that, too....
Other things I've thought of and mentally rejected but wanted to mention...
Ghan-buri-Ghan's people...the builders of the Pukel-men. I can't come up with a good name, though.
Angmar -- real kingdom in the second age, but their leader is really a Mordor GL and it's one age only and....
Aman -- should not be accessible. I like "Voyage to the West" as a win condition replacing space race. [Especially for First Age scenario.] So Aman/Valar is OUT as a race/civ.
Empty space? I think there should be some. Middle Earth was distinctly not filled with sprawling metropolises and covered corner-to-corner with cities. Much land was still wild and "untamed" and barren. The Third Age scenario I envision has quite a bit of empty space and settlers HARD to make. The First Age scenario shouldn't be as empty, but I have fewer civs listed -- probably each is very powerful, however. <shrug>
Of all my rambling ideas after the list, I think the best idea is the "Forces of Nature" civ. Maybe even make it human-playable, but I'm not quite sure how that would work.... Sorry this got so long.
Arathorn