I've been thinking of the most crazy SG. And I got an idea. It looks like this:
We pick an AI civ, and it must win! This would probably be the first civ we meet, or manually chosen, it doesnt' matter. But if we win, we lose, if somone else wins, we lose. The SG is won only if the target civ wins.

Do you like it?

Hmm, sounds weird, but too easy.
Domination - just give them enough cities
Conquest - just give them all cities except your capital, diband all units, and declare
Space - just make sure no other AI gets far enough
20k/100k - nothing you could influence

Diplo may be the only remotely interesting thing.

I think there may have been a similar RBC SG. I'll look later.

RBD19-The Return of Big Brother (http://forums.civfanatics.com/showthread.php?s=&threadid=43926)
In the end, Persia, the "little brother," won by space.

I've played one where I role-played the characters in CCS. I was Tomoyo, obviously, and I tried to get "Sakura" to win by diplo. There were certain civs labeled that I had to destroy or protect.

No, of course we would not be allowed to give them anything. So military ones will still be hard to achieve.

And you could even have some influence on cultural ones: declare war on anyone building a wonder. (only the likely ones). and if we make the little brither big, he will probably win anyway.

I'll starts a SG if there's enough interest.

Edit: What difficulty should be? I guess Monarch, or Emperor.