PeterH:
I guess I don't understand what you really want to achieve, then. Are you also going to relabel the keys when you switch the keyboard between different layouts? If you only translate the scancodes and leave the original key labels in place, I would have thought that would be extremely confusing.
The labels on the keys have no meaning for me, because I never look to them. But using a keyboard I would like to expect the English-Dvorak layout, because the switching between Qwerty and Dvorak is confusing. So only translate the scancodes is absolutely enough, it is also usual, because most keyboards I use have other labels as configured layouts, f.e. mostly they are english and sometimes also russian layout but with german labels, because here in germany it is difficult to find a english or russian labeled keyboard 