I'm envisaging an 'account manager' group, who would be able to view and edit the profiles of other member groups ONLY if they were in the same category.
Different organisations each have multiple employees using the site, and a manager from each organisation needs to be able to edit their employees' details. So the categories would be organisation names, which allows the creation of a User list for each manager, showing only members in their category. They click through to an edit form, which of course should also check that the member really is in their category.
Of course we could create multiple member groups to achieve this, but there are hundreds of organisations, so that's not really an option.
Does this sound feasible? Any security flaws, for example?