I too feel that the diplomacy screen is lacking. Right now, for the player, it's pretty much about trade and treaty. We can't suggest to other races the Race "X" is a threat, and it would be great if they chipped in. We can't demand the surrender of race. We can't respond cleverly to tribute demands, although in my mind, my diplomat rolls his eyes and walks out of the room or hangs up the Galactaphone when I click the "Reject" button.
It's gotta be built into the system already; how else would the AI be using it? Maybe in 1.2
I've surrendered three times. The first surrender was an accidental one to a minor race. The second was just a game I grew bored with. The last, I was being attacked on two fronts by the two largest and most militarily powerful civs. I was holding the line until I lost a gambit for a planetary strike. My invasion fleet was wiped out and I lost a key production world. I saw the writing on the wall at that point and played for another 1/2 year before surrendering to a race weaker than I was to screw the aggressors.
