Such a user you can give a one-page-upload-URL:
As user fex call:
fac -u goofy@stupid.netfrom its output select the URL which looks like:
http://YOURFEXSERVER/fup/jhghbFTYAty673hgdfHy76e7bye5pLXN0dXRkjyrd6776bkhy288
and add "?FEXYOURSELF=yes" →
http://YOURFEXSERVER/fup/jhghbFTYAty673hgdfHy76e7bye5pLXN0dXRkjyrd6776bkhy288?FEXYOURSELF=yes
and give this URL the goofy user.
He then just has to select a file with his webbrowser, hit [upload] and READY ☺