Like for example, lets say Mao and Stalin are raging against Churchill so Mao opens up the diplomacy screen and instead of bringing Stalin to go to war against Churchill, there's a category of like "Joint War" which forces both Mao and Stalin to declare war on Churchill. And if Stalin doesn't wants he could, but probably wouldn't (since he too hates Churchill), ask for technologies or gold from Mao.
Or like Catherine wants to attack Shaka but he's wary that Pericles, who's impartial to both, could be bribed by Shaka to become a war ally, so beforehand Catherine signs a non-aggression pact with Pericles. And then Pericles takes advantage of that by declaring war on Ghandi etc.
Would make war more interesting/dynamic/realistic imo
Or like Catherine wants to attack Shaka but he's wary that Pericles, who's impartial to both, could be bribed by Shaka to become a war ally, so beforehand Catherine signs a non-aggression pact with Pericles. And then Pericles takes advantage of that by declaring war on Ghandi etc.
Would make war more interesting/dynamic/realistic imo