Big thanks to everybody here !!!!
I did the upgrade as outlined here and it worked like charm; everything works like before (IO control, Fantom, VS EXPAND, control surface, ...) but now running on win10 :-)
Excellent info here, regarding best workflow, driver mods, driver signing on/off ... and also the wait you might encounter when installing the VS-700R.
BTW, I did install the VS-700C driver first (which I had not used in standalone mode by itself up to now) and just ran the surface with an Octa-Capture as interface for a while. Then I installed the VS-700R the usual way ...
So now if I want to run without the VS-700R (which may eventually happen), I unplugged the custom I/O cable from the VS700C, plug the USB cable and flip a dip switch ... so less than a minute to go VS700Rless.