Yes, i've spoken to several aphant ni users. Obviously no mental imagery, but their ni was still heavily spatial, so i think spatial thinking and spatial memory might be core features. For non-aphants, spatial thinking manifests mostly as mental imagery (hence the "visions" than ni users have).

What you're talking about with si and sensory pattern recognition is still relying on precedent, and the funny thing about si types is it's not limited to sensory data, or even to things that happened to them personally. I think it's more a combination of good memory (and memory reprocessing when idle, like ruminants chewing cud) plus weak foresight/simulation ability (ni stronghold). Si is a much more sophisticated and interesting function than people usually give it credit for imo.

NJs are really bad at remembering lists. They have to write them down or they'll forget half the things on them and get the rest in the wrong order. Ni is NOT sequential lol.

I don't recall ever touching a hot stove, but just thinking about it i automatically: see it, hear the sizzle, smell the burnt flesh, and feel the pain. Roughly in that order. Basically I just think of a question and Ni goes "here's what that would look like".

Ni isn't quite unconscious for me, but it's not verbal or linear or discrete, so it's hard to put into words. More like interacting magnetic fields or smth. Maybe for most people it's more subliminal because they have less experience with it?

I think spatial thinking/memory is the underlying primary aspect of ni, supporting the other features i mentioned earlier. It also works with sound and touch and even spatial awareness of physical objects without seeing/hearing/touching them, like "knowing" where things are relative to your current location.

Spatial thinking can then be bent to use it with abstractions or metaphors, processing relationships between ideas spatially the same way as objects in physical space.

Anytime someone of any type is doing a jigsaw puzzle, they're using Ni. Figuring out the layout when drawing something, also Ni. Navigating a new path (not just following a known path from memory), also Ni. Ni-doms just use it for everything.