[setr]

You want it to behave predictably. That doesn’t mean it needs to be predictably incompetent, and it doesn’t mean predictably optimal. Predictability is orthogonal to competency.

If the diplomacy mechanic cannot survive with players playing to win, then it’s clearly the diplomacy mechanic that’s wrong — diplomacy in reality is an inevitable result of multiple players playing to win; you don’t do diplomacy for fun, but to shift the world-state slightly in your favor by unifying against common threats.

Something must be fundamentally wrong with the model if it cannot encourage the most basic action within that model, without a player acting completely against his own interest