Having one step-by-step guide to save much time for seeking the not mentioned details ...
Any updates or changes to the template of your service qubes imply the risk of a hidden error, making your service qubes unbootable. Repairing this without having access to the internet for information or guides or without having a working mouse can be really time consuming. - I know about this ... ;-)
Building a separate template for each service qube is space consuming, as the system-disk of each template will use about 10 to 20 GB.
Using a mini-template as base for the sys-... qubes reduces the number of packages and therefore the needed space.
That's the reason for my approach, one sys-mini template for all service qubes.
The work is nearly the same wether using fedora-xx-minimal or debian-xx-minimal. I've used both ways (both are working), because there are different packages and guides for addons to the service qubes, some based on debian, some on fedora.
Now we'll create a named disposable template as base for each service qube.
It's ok to use --label black for sys-mini-dvm, as it is as safe as any other template, if you don't expose it to the internet.
The next steps can be done within the Qube-Manager.
Be aware: Your old service qubes are still running and many global settings depend on them. We will not touch them, until we are sure the new qubes will do their work. That's why we'll create the new qubes with "-new" appended to their names.
click "New qube", use "Named disposable"
choose "sys-net-new" and click "Settings"
click "New qube", use "Named disposable"
choose "sys-firewall-new" and click "Settings"
click "New qube", use "Named disposable"
choose "sys-usb-new" and click "Settings"
Keep in mind: We havn't changed any global settings. - During the next tests we will have some problems with using usb-devices. - It will be no good idea to use the Update Manager. - sys-whonix shouldn't be started, as it still depends on your old "sys-net" and "sys-firewall". - Maybe it's a good idea, to save this guide locally, as you'll need to stop all virtual machines connected to the net!
Stop "sys-net" and "sys-firewall".
Start "sys-net-new". - If sys-net-new declines running, most probably one of your network devices needs "strict reset". - If the Network-Manager-Applet appears and you are able to see and connect your network-connections, all is good. - On any other problems recheck the steps before. ;-)
Start "sys-firewall-new" - change the network setting of "personal" (for example) to "sys-firewall-new", start it and check if you can reach the web! - On any problems recheck the steps before. ;-)
Stop "sys-usb" and start "sys-usb-new". - Your devices should get disconnected and should reappear now connected to "sys-usb-new". - For me I got a system message, that my usb-mouse and usb-keyboard were declined for input to dom0. - That's normal! - On any other problems recheck the steps before. ;-)
If until now all works as expected, we've done the main work. Now we can change the system to fully use the new service qubes:
Open the "Global Settings Manager" and check if all settings point to the correct quebes. After this your usb-mouse and usb-keyboard should work correctly even in dom0. Maybe you'll need to restart "sys-usb".
Start the Update Manager and make a full update to see if all these settings are correct.
Last check: Restart your Qubes System! - It should run without any problems.