Using user specific root_names in templates

(Sorry in davance if I missed this in an existing topic.)

In our next project users should be able to download a zipped project and extract it to a place on their personal machine using a tool launched from SG desktop.
At this moment I’m looking for a way to set up some templates in SG toolkit to have the work/publish files on our server (connected through VPN with a fixed name; the primary File Storage), and on the other side to use templates to manage the local filesystem (a secondary File storage specified by the user; so we can fetch all the needed info, and publish back to the server)

At a certain moment I found out that it is possible to use env vars (like SHOTGUN_PATH_WINDOWS_SECONDARY) to specify the root folder for published files if these paths are not specifically set in the File Management. Is it possible to use this in the toolkit templates too? (there is a root_name in templates, so I assumed it might be connected)

Or is the only option to set a custom drive (like P:) and link it to the chosen folder of the user on the personal machine? (personally I would set it up somewhere on my “D:\Work.…” for example)
Or could I try to update the roots.yml on the personal machine with a script when SG desktop is launched?

Links to the things I found (and tried):

If anything is unclear, feel free to ask.
All help or experiences are welcome, I’ll update this topic if we find a more elegant solution.