Is it allowed to assign the same range of subordinate user and group IDs to different users on the system defining the subordinate IDs?
Please provide sources for your answer.
The idea here would be to make use of something like
lxc-usernsexec from an unprivileged user account as well as having root-owned userns LXC guests that can be autostarted. I.e. the unprivileged user should be able to impersonate the same subordinate IDs as root.