Try Pong, it's so simple and equal for both factions that balance is perfect and works fine in single player and multiplayer.
Yeah, sure, just have one set of troops and techs and all race and faction is would be just fluff and color and backstory.
Yeah, it'd be balanced...but would it be fun?
Heck, why not just have 1 kind of unit in the game. Perfect balance, no?
I admit I don't play a lot of multiplayer - but when I do play for the few RTS I have, I wouldn't want everyone to just be running around the same troops just of different model and color and name - but really they are all the same.
Sounds boring.
I think the only real problem with DC is that it's actually a tangible, trade-value resource.
If it were intangible like the expression "political capital" that presidents "get" when they have such strong support of the people - then I think it would be a lot easier to visualize ideas for. But since it's basically another kind of money but with no value behind it (what is 1 DC actually worth) it gets hard.