sys-usb is disposable, which means that when you restart it, it goes back to its original state, so as long as the template (and the controller) are not compromised, that shouldn’t be an issue. To further mitigate this, you can create a sys-usb-2 and assign it a different usb controller (if you have it).
It’s not recommended because then you’d have direct access to dom0 through a usb port.
# Get the template used for the current sys-usb
[user@dom0 ~]$ usb_tmpl=$(qvm-prefs sys-usb template)
# Create the new sys-usb
[user@dom0 ~]$ qvm-create --disp -t $usb_tmpl --prop netvm='' --prop provides_network=True --prop virt_mode=hvm sys-usb-2
Finally attach the usb controller of your choice as I explained in the last bit here: WiFi network missing from Connections - #2 by BEBF738VD
Tip: to get a list of available USB controllers: qvm-pci | grep USB
Note: if you want both sys-usb and sys-usb-2 running at the same time, you need to detach from the former, the usb controller that you attach to the latter, otherwise one of them won’t start.