A great thing would be a Diplomacy mode added to FFA and Teams. This would enable people to add others to temporary teams when forming alliances and to make it so that you can airlift an ally, transfer to an ally and have to wait for at least 1 turn after disbanding an alliance to attack them. This would be good for hosts in diplos to control the amount of allies people are allowed to have. Declaring war on someone could be something official by clicking on their name and then clicking "Declare war". This would allow everyone in the game to know who is declaring on who and enable people to attack the next turn and not cheat.
I’m pleased to announce that peace treaties / diplomacy games can now be played using the new mod framework!
Check out the mod “Advanced Diplo v2”, which has a war/peace/allies system, and a lot of other neat features that work with this!