The market positioning of a sensor like this would be something used in every R-mount consumer camera, much like APS-C EF-S sensors are now. This way there would be a clear market delineation between EF-M, consumer level aps-H, and Pro level. If they did a 1dx speed camera using the smaller sensor they'd probably price it/name it as a more expensive 7d type camera to differentiate. A smaller sensor with a lower pixel count would be faster offloading data, and would require less cpu computational horsepower to determine focus and display in the viewfinder. I'm thinking something like 26-28 megs. Most likely the next pro full frame R camera is going to have much more than 30.
But my point on this is that it would be a whole line of cameras, all using the same R-Mount lenses. Probably priced a little higher than the current line, because it's a "step up" from aps-c, but not as expensive as full frame. My main reasoning for this speculation is simply because Canon likes to differentiate the market, but at the same time this gives them an actual improvement above competition. This might also explain why the R came in at a price higher than everyone expected, simply because they wanted room underneath it that allowed price increases also. People would balk at a R version of an APS-C 80d at 13-1400 but they would probably be ok with that price increase if the sensor was larger.