What if you got another keyboard to use for SketchUp? Get one with a full size Esc key. You could certainly do that sooner than waiting for the software to be changed to suit your request.
I wrote a script that adds a “Cancel Operation” menu item that sends ESC key.
Once added to the menu you can assign any key chord accelerator (shortcut) you wish.
It is funny. I use the Esc key quite a lot and, on a Mac keyboard, it is just as small as the Japanese version. I probably do hit the key below it sometimes by mistake but maybe it is not as bad as hitting the IME key.