There is actually an advantage for Canon here. Their EF-S has already got a shorter backfocus/registration distance, which other camera manufacturers with mirrored APC or full frame systems did not take advantage of. That's why EF-S glass has bits and pieces that stick into the mirror box, making it physically impossible to mount on FF cameras like the 5D even if you remove the baffle (been there, done it, smacked a 60 macro on my 5D's mirror). But they could leverage that for their newer smaller cameras.
I'd buy it as long as it took EF/EF-S glass. If it can be adaptered to do so, then by all means. ie. a hypothetical EF-M (micro) mount with EF/EF-S adapters and its own EF-M glass. I'd consider it even if it was a 2.0x or 1.8x crop. So happens, EF-S 15-85 IS USM with a 1.8x imager would fit nicely into my preferred zoom range, being 27-153. And the 10-22 would still be 18-40, still plenty wide.
The nice thing about such a system, if it was compatible with existing EF gear, would mean choice. I could pack a smaller body as a secondary/backup camera and still retain choice of lens. Then when you want to break out the big telephotos you can always take another EOS body.... maybe a 7D or 5D with the Brick Grip (no screws needed, just duct tape a big cement brick to the bottom of the camera.)