This is, partly at least, what I've been working towards in my studio practice, minus summing to stereo. I work with parallel loops, applying frequency banding in the manner you describe, but spatialize within an eight channel dispersion environment. Rather than using autopanning, I use a reactivision based control surface to pan within the space. At the moment it's part theoretical, part practice, and all experimental as I move towards integrating the whole thing into a working system. Of course working with parallel signal paths opens the door to other forms of pannable filter streams, and that's where I ultimately want to take things. I hope to get some studio time in the coming month, but time is, as always, a rare and precious commodity.