Can we somehow patch the clock to show a local time zone while leaving system time time in UTC?
This most likely requires a Whonix Greeter first so that we can get the timezone from the user.
It might be possible to configure the clock in the kde task bar. Time zone in kde clock can be changed without root rights and without affecting /etc/localtime, thus the user can have it's clock show what she wants. It looks like this is either configured in /home/user/.kde/share/config/plasma-desktop-appletsrc and/or /home/user/.kde/share/config/ktimezonedrc.