First-off the one I've fleshed out the most conceptually:
Canada - John A. Macdonald - Symbol is a maple leaf of course, colors are blue on teal as in the current municipal flag of Ottawa (originally went with brown on green with the triple leaf symbol of the Ontario coat of arms, but the scheme is too similar to India's)
Multinationalism - Upon establishing a Defensive Pact, gain the other civilization's Unique Ability, and allow that civilization to do the same.
(that civilization does not pass on that ability as well: if Canada establishes a Defensive Pact with Byzantium, Canada may gain an additional belief, and if Byzantium then establishes a DP with Siam, it gets those increases in CS yields, but Siam will gain nothing unless it has a Defensive Pact with Canada as well. Basically this establishes mutually beneficial and extremely powerful diplomacy blocs, with Canada and their allies reaping the benefits from each others' UAs)
Unique Unit - Mounted Police - Replaces Cavalry. Unlike the unit it replaces, it removes 75% of the
Unhappiness of a city it is garrisoned in.
(It does
not pass that ability upon upgrade: you may not have a super happy Landship Police. It presents a choice: keep Industrial-era melee units stationed in your cities and be super-happy, or upgrade them and lose the smilies to defend yourself better.)
Unique Improvement - Igluit - May only be built on Snow and tiles adjacent to it. Available at Construction. Provides +1
Production,
Culture, and
Faith to the nearest city. Does not require a
Citizen to be worked.
(They do not need to be in your territory to provide benefits, they will give their bonuses to any nearby city, if two are in equal range it will give them to the smaller city. They do the same even if the city is not Canadian. This is basically the Inuit compromise >.>)
On one hand, I basically think a good expansion concept would be the four big modern nations alongside five of the six yet-to-be included veterans (either Mali or HRE would be cut, I'm leaning towards Mali as the Songhai basically covers it, but then Austria practically covers the HRE in execution). On the other hand, I think those two sets would make better DLC than anything, and nine entirely different civs be put into an expansion. Of that, I guess I have nine picks for that, in attempt to be balanced and fit with the theme the expansion will require (being inevitably science-oriented, as that's the victory that requires the most work):
Norway (remove all Denmark's Norwegian stuff, give them the Ski Infantry and the Stave Church)
Kongo (by and far the most viable new African entry)
Chile (solid enough South American choice, IMO)
Georgia (easily the best choice for a Caucasus civ, plus it has a solid female leader, Tamar)
Vietnam (overlap with Khmer if they are indeed included, but it is definitely popular here, and the Trung Sisters would be awesome)
Malaysia (A bit of SE Asian dominance, yes, but there's a lot to this region, and many different eras of Malay people to possibly cover)
Mughal (A very huge and dominant empire that's probably a long time coming.)
Hungary (also pretty popular, and could be done well with)
Holy See (basically the concept for another weird civ, the idea would basically be amassing immense power from religion, primarily Production for followers in other civs, and gaining rewards from following CSs even if they aren't your ally. Probably would be a bit odd and controversial, but could be interesting)