If we are to actually go anywhere with "Declaring War" in terms of nations, I believe it should be integrated with an existing chain of issues that NationStates already has: An International Incident. However, the only difference would be that the nations would both be affected, with the bare minimum context added, and possibly some changes to the issue chain for the sole purpose of Declaring War. It would be fun, but purely NS, and satisfiable to the angry masses yearning for War.
Thoughts?