I was thinking sometimes it's a shame that we can't arrange secret treaties, when it would be really interesting and fill the game with intrigue. As I see it, the main problem is multis and abusers, right?
Well, I guess a solution would be to allow them, but only in a "random lot draw" only, or maybe in specially arranged tournaments.
I mean, sometimes you sign a treaty with an ally but you realise that ally is becoming too powerful and you can't backstab him yourself. It would be intriguing to try secretly make peace with your old enemies after a bitter war, for example, and your ally doesn't suspect a thing ... yet.
This to me, would be a very nice aspect to those who want to play that way, especially since this is how things operates in the political arena. It's a shame that they are forbidden only because of abuse. The entire world structure has been practically been formed from the secret alliance system before WWI, which led to the alliance system in WWII, which led up to the secret alliance funding of various Middle East groups.