Is there a reason why the MX Master 3 main window is so large, not that I mind, but seems a bit OTT for the mouse diagram with the button functionality.

Also for MX Master:

snap on/off carapaces to adjust for size of hand. Also to clean

Offer a L-handed version.

Reduce work of the scroll wheel by concentrating mass nearer the outer rim, possibly with brass or lead. Could be recyclable if entire mouse can be disassembled.

Reduce base friction with teflon pads perhaps

Lower the mouse's centre of gravity.

Thumb wing button slightly over-firm/undersensitive.