- Location
- Yes.
I know I'm breaking an unofficial rule by saying this, but while the mechanics of the quest are built to fit the narrative and can be violated as needed, the mechanics are meant to fit the narrative, and we can make assumptions based on this. Like the fact that a ninjutsu capable of detecting ninja from (by my estimate) thousands of Zones (meters) away would be so prohibitively chakra-expensive to cast that the user would be dead. Or the Sot6P, or maybe a Jinchuriki (I'm not going to believe a Jinchuriki is here, that's just insane).The issue in that reasoning in my opinion lies in that we don't know if there's anything for which chakra diffusion could not be a problem (e.g. fires can spread past the range of a fire ninjutsu, what do we know about signals, if someone has an enhanced sonar thing or whatever), be bypassed (e.g. something done long ago established a connection between them and there, and the link functions more as light from a laser, diffusing a lot less), or be irrelevant (another effect grants the same bonus, e.g. Byakugan lets one see better far away even if the user doesn't have any means of sending chakra up to where they can see, because they don't need to. A telescope does essentially the same job without sending anything anywhere). Shikaku himself assumed it was possible to overcome, bypass, or somehow render moot that issue for "point defences", that is, a fully operational counter at extreme long range for Skywalker-enabled suicide attackers instead of dismissing the idea entirely, back when the concept was first introduced.
But on a more narrative standpoint, if we had a ninjutsu capable of detecting stuff from thousands of meters up (I will use your sonar as the example), I have difficulty seeing how that ninjutsu user could get any meaningful information from it. They would get "Something is here. Is it a bird? A magical flying ninja? An annoying wind spirit that messed with my ninjutsu? Who knows?", IMO.
The rest...Please do not take this as an insult, but I have the feeling you are making arguments that could possibly make your conclusion valid, and not analyzing how likely they are to actually be true. A connection between the ground and the random patch in the sky we are in is possible, but it raises questions like "Why would they do this?", for example. I certainly acknowledge these things you have suggested as being possible, but I don't think they are likely enough to warrant consideration.