1: Decisions have inertia. We are very firmly on the 'murderize Akatsuki' track.
2: Getting Leaf to negotiate is a absolute non-starter because Akatsuki murdered a Hokage in broad daylight.
3: Oro would only go for it if there was a solid argument for it, which i'm not seeing.
4: What would even be the line of negotiation? We're trying to ambush them, not like we can go "You should surrender because otherwise we'll ambush and kill you".
1. I don't think we are actually that firm on the track. We went missing nin to improve our power. And to kill akatsuki yes, but if we don't kill them the runes still improve our power. And socially ninja expect the people who diplomacy with them to want to kill them anyway. The major villages with each other. The major villages and Akatsuki. Leaf and Akatsuki after they killed hokage/kakuzu.
For inertia, situations change. New information and context is obtained. Even failing to obtain new information that one was hoping to obtain but did not expect is an update (such as researching a rune giving high odds of beating akatsuki, and minimal consequences from failure). One should be adaptable.
Yes there is a factor to consider to not just flip flop on strategic goals between every voting cycle.
But I think in this context it is reasonable to at least discuss and brainstorm and think about whether fighting Akatsuki is worth it. The pros and cons. To think of what alternative options there are. IC. I'm not sure how much we did that OOC either. Originally the research mission was to see if we could make runes that would make fighting akatsuki worth it, not a committment to fight Akatsuki no matter what. Then Naruto told us to go missing-nin, and I don't know how much we just went with the flow on that. Now we have made runes, but I don't know if there was a discussion on if we have made enough runes.
2. Leaf is part of AMITY. They have not gone on a war with Akatsuki without us. They refrain from attacking the other major villages who are their mortal enemies. Tsunade previously thought it was suicidal to attack Akatsuki. If we can convince them negotiation is necessary for survival, then it's doable.
3. I dunno if you saw my edit. But we can require our support for the assault to depend on trying diplomacy first. We can say Leaf might not be willing to support us, if failure means their destruction. We can say that diplomacy can get him a better chance of what he wants (if we can convince him that the odds of Pain following AMITY instead of doing another moon plan. Is better than the risk of him failing the assault, Leaf getting nuked. And after his immortality resurrects him it's just Oro alone against Akatsuki).
4. The point is to brainstorm. One can't expect to have a great plan before putting any effort into it. But we could say we will tell the other major villages that Akatsuki is gonna monopolize an afterlife rift. We could say if leaf attacks them they would obviously offer the other villages whatever they want to support Akatsuki. So why not skip that and just offer Leaf whatever it wants for cooperating with Akatsuki? We could say if they preemptively kill Leaf, we will tell the other villages what Akatsuki has done. And if they instead increase their security in preparation for an attack. Leaf can delay it for a while. And that extra preparation means Akatsuki has less manpower for searching the rift, making it taking longer to find Pain. A longer chance for Pain to dissolve. Leaf could offer it's own manpower to help find Pain. Or to convince the afterlife inhabitants to share information about Pain, with the idea that everyone is united and on the same side after death. It looks a lot different to the afterlife people if a coalition of people are trying to resurrect people. Instead of the old factional loyalties.