If the server is a VPS at least, it is possible to Docker container to shove a whole and for each new volunteer to create.
If You must strictly adhere to the conditions, ie as admin, but just nothing that would be impossible to do something rights to files and folders expose read-only (good case) and accordingly for the database put the appropriate rights to the table (some still have to give the entry in the service order WP).
If necessary, that would have been more just and admin which are all possibilities, as far as I guess the easiest solution would be two copies of the site (for example, on the subdomain) on one base (when connecting to the database in the settings only make the different users that would have a real site as usual, another site at least).
demario.Auer answered on March 23rd 20 at 18:44
We usually allow people to play in the sandbox. Or really in Docker container raised by the installation script temporary.