vchown?
is that like virtual-chown?
Sounds like no root for you.
And in that event, you'd be best off writing a shell script of some sorts that could control vchown and delete the files for you via a crontab setup.
And to answer your other question, nobody can login as nobody...
%pw user show nobody
nobody:*:65534:65534::0:0:Unprivileged user:/nonexistent:/sbin/nologin
...Unpriviledged user nonexistent...
That means a lot to Unix, it means it has no login, it doesn't even exist except to the process it serves.