Diplomacy games are quite popular, but the diplomacy system is really bad.

I hope that it will be upgraded and suggest something like the system in Empire Earth 2 with suggestions for peace treaties and alliances that the other part must accept to have the stances come in effect. Terms could even be added, as the AI originally does: “Send me 500 of each resource”.
It should possibly be an alternative option as some scenarios (among them one of mine) uses the weakness of the current system.
The diplomatic stance of Neutral is also a very useless stance as I see it.

Someone on the forum (sorry for not finding it) also suggested the possibility to share control of units, optionally upon DC.

It would also be nice to have access in game to information on the diplomatic stances of other players. Knowing who your ally is allied to can be very useful in a game of diplomacy.