an ideal stance for me is where you can adequately respond to an attack. if you are in the street and somebody suddenly attacks you, do you have time to go to kamae? I doubt it. One of the few colleagues I've been training with whos also has been in a lot of streetfights also doesn't like his would be opponents to know he knows martial arts or that he's intending to defend himself by going into a kamae stance. Going into a stance would give it away and make his opponents more aggressive. so I think launching a response from a no stance is more realistic. Timing for the response/blending for an attack is more important IMHO. If your timing sucks, will your kamae save you?
I like it. For practice purposes you can learn the different kamae, whether 'square' or 'natural' and if you really study them both you can learn a lot.
However, once the body is used to moving in such fashion then the emphasis changes. As an example I would say you are now learning to move from centre without having to focus on which foot is where as they will naturally move.
So as you say in the street if someone attacks you from the side then at that moment you are in a sideways on kamae. I bet no ones been trained in that one. ha. ha. It's now about moving and blending with whatever is there and is more to do with the factors you describe.
All things have their right place and right perspective.