How best to let non-developers "rank" tickets?

Our small developer group has difficulty keeping up with the changing priorities of other business units. Our idea is that we give limited logons to Redmine to other business units to let them somehow "rank" the tickets that are relevant to their group. We already have a custom field to track which group a given ticket/bug/feature request came from.

I don't really want them able to edit other issue details.

Any ideas?