Guys...
How many times to I have to post the Starcraft argument? It seems like I have to go to every thread where some person decides it's a great idea to complicate the game even more without paying attention to balance. I'm not going to post it again in great detail here, but I'm just going to say with more than 20 civs and more on the way, less is more when it comes to uniqueness. Starting technologies, 2 traits, unique units, and unique buildings are enough--don't make the game any more of a balancing nightmare than it already is.
One of the reasons I think there is not a Seafaring trait in Civ4 is because of the trait in Civ3--it was very situation-dependent. As in, if your map did not have water, you essentially played with 1 trait. Adding this as a unique ability to, say, the Vikings, would not be fair--what is the use of going into ocean squares and then darting back to the shore if there is no ocean? And how about the fact that galleys, triremes, and ironclads are all move 2 units (or more with promotions that are available after Flanking I)? The fact that terrain is mostly irrelevant of your decision to play any given civ is a good thing (at least my decision is...some might say with the Aztec/Celt UU abilities, they do). But that's a small fraction of the whole.
Seriously, free communism for China at the beginning of the game? That sounds a little

. Considering the Soviet Union was the "original" communist state, that sounds a little unreasonable. But wait, if you focus on the communism, how will you represent the age of the czars? Or the Chinese emperors? How will you reconcile these two distinctly different periods of their history with one national trait? Here's a bright idea: give them at least 2 different leaders: say, one relatively modern communist, and one from the more distant past. And, say, these leaders have different traits representing their focus and what they did in power...wow, isn't that great? And guess what, it's already in the game!
How about you just make the Scottish leader (if they get added to the game) Aggressive to give their units Combat 1 instead of artificially adding it separately? And Spain isn't the only country to persecute other religions (although they seem to be the most famous for it).