I was thinking that it might be an interesting option for the future, and that it wouldn't require a lot of programming work.
Two against two, and those who go together share their culture at the end of the game. The pacts might not make sense, but there might be some small option to lend military force or give resources to an ally. Anyway, I can think of many possibilities, but I think it could be something very interesting without hardly changing the game. What do you think?