Yes, the “you are moving” feedback is quite crucial, at the very last for game feel. I want to know, that if i press something, that something is happening. If you omit it, you’re basically saying: “I know you can’t see or hear anything happening, but trust me, you are moving!” Which is very strange. It also just feels strange, because in the real world, everything makes a sound, so having something happen, without making a sound, is very wired.
Apart from that, it is also important to let me evaluate walking distance. I can now build a map, depending if i hear one, two, or three footstep impacts, on how far i have walked. Even thou this might not be exact, it still gives me some feedback for evaluation.
You said, that in order to dodge bullets you just need to make a step to the side. I always tried this but it never seemed to be working. The reason might be, that i’m walking too much. If i have footsteps sounds, i could now determine: If i hear one footstep, then i have walked enough, if i hear two footsteps, then i’m already in path of the next bullet.
As for directional bullet sounds, i don’t think this would lead necessary to problems, if you have a proper volume by distance curve. You ofc also might need to scale down the amount of bullets you have for the purpose of a audio game. If you would have 16 bullets in visual bullet hell, maybe here you do only 4 or 6, and i think this would be fine. But one would have to try, to know for sure ^^
I like the idea with the 9 quadrants, so you can get a better feel of the arena, that sounds interesting. Maybe 9 is a bit much thou, 4 might be sufficient. With those you could have a bit more fine-grained info where the boss is in relation to yourself.