So, if the title wasn't a hint, I'm curious... do you, the playerbase, want an inter-village Ninja World War?
If this were to happen, people would be open perma to cross-village shinobi, and people would start actively working against one another instead of all being in the same place and being happy go lucky. Village travel would be restricted, etc... but there'd be obvious conflict between the villages and it'd be something that wouldn't necessarily need a DM to oversee every single thing for there to be conflict.
Thoughts?