So right now, comparative reach matters. That's all I was saying.
Don't spend too much time trying to kick in open doors.
I don't really think there is any significant cost difference for having a larger shutter. All cheap film bodies had full-size shutters. The big difference is that we now have much better electronics to control their operation. A modern camera measures the actual performance of the shutter so it is auto-calibrating the operation.
A bigger mirror will result in a bit more sound - and will affect the maximum frame rate the camera can manage and still make use of the phase-detect auto-focus between each frame. But Canon can produce 10fps capable mirrors and can decide that 10fps is only for more expensive bodies.
And the theme of the thread is a random view that Canonw ould drop the crop-factor bodies. And there are currently no good economical incentives for such a move.
But the original post I made that seemed to have trigged you, focused on the fact that it isn't the sensor size that gives more reach. So there are no specific reason for selling smaller sensors just to give reach - whatever definition you want to use for "reach".
The magnification of the viewfinder isn't hard-coded to the size of the sensor, as can be seeen by different camera bodies having different magnification/coverage in the viewfinder even if same-size sensor.
And the amount you can crop/magnify the photo is related to sensor pixel size, and the quality of the sensor. Making the sensor twice as large would not reduce the ability of the sensor to get as many pixels on the bird, or get the same quality from each pixel.