"Bloviate" Niiiiice!
Larry, I'm intrigued. You make compelling arguments.
My knee jerk reaction is to agree with Peter about the imaging part. The Blose example (as well as the Def Tech bipolar designs, and the electrostatic/ribbon products) infer a very significant amount of direct sound in addition to all that diffusion. But you could possibly "get there" with the QS8's too, *depending upon placement*.
I think the satisfaction level with this setup would be extremely dependent upon room boundaries and placement. I know, I know, everybody says that the QS8's are very flexible, but that comment relates to their primary use as a diffuse surround speaker. Using them as mains would pose pretty different challenges, I think.
Second, your observation about the bass extension is a good one. Somebody who has been posting a bit recently alleges that all bass above about 60Hz is quite directional to his ears. I frankly don't know where the line is, but I think it is safe to assert that sound gets more directional the higher the frequency, up to a certain point where only my dog can hear it. Anyway, maybe if you used stereo subwoofers that would alleviate some issues there, albeit at a price. You'd certainly need subwoofers that had good response at a higher range than you're typically evaluating.
I do have some frame of reference here, which may be encouraging. My current setup is a longish, narrowish room where the listening/viewing area (and the QS8's) are halfway back (it is a living room / dining room combo). So, when we're on the couch in the living room, the surrounds are in a good spot and it's all lovely. But here's the thing - I often listen to music in 5-channel stereo, and when you're sitting at the dining room table, the QS8's are the primary perceived source (rather than the M60's, which are 18 feet away). It really sounds pretty darn good, and I've been happy about the unintended benefit of extending the quality of the "stereo" the length of the room.
In summary, why don't you just TRY IT and report your findings back to us
