Hm. Not totally sure... I just started messing with this, but...
I think what you could do is connect to the VPN and sync the latest state of the repo, code, issues, patches. Then disconnect from the VPN. Work. View issues, review patches, write code, git push to your local node. Then, when you're ready, connect to the VPN and sync up with the latest changes.
Or I guess you could use the VPS as a bridge? Install Radicle on the VPS, which is also connected to the VPN? Sync your local node with the VPS node?
Just gotta make sure the repo is set to private so it doesn't get announced to the whole network. A private repo is invite-only.
Hm... Idk. Again, total Radicle noob here.