Originally posted by Sandy Hancock Minox made a pretty small 35mm camera too, and the Olympus XA was very popular I even had a tiny Pentax (PC35AF) back in the 80's, but was there ever a 35mm ILC of comparable size?
I believe a FF ILC can be made almost as small as Q cameras of today, but because of the sensor/lens mount size a FF ILC will be higher in size than Q. Sony made a very compact FF camera in RX1, and I believe a ILC can be done of the same camera body size.
Sony A7 series is not about smallest possible size, but more of smallest practical size used with lenses available for them today. If Sony ever put priority on make small FF "pancake lenses" for FE-mount, there might also be a reason for making a very small camera to use the lenses on. Remove EVF and grip from A7 cameras and minimize the size in all directions, and it will not be much larger than Q series cameras.
A problem with Q is that the lenses is quite large compared to sensor size. I'm surprised that there are no lenses for Q that fully use the advantage of the smaller sensor. A collapsible pancake standard zoom would make a lot of sense on Q.