Approval Group Selection

System

I need to have approval by OS group rather than approval by a user (such as the workarea owner). I am working on an Intranet and most of the content is in a single branch. It really needs to be a casual contributor/ad hoc system (with portal integration, so the user browses the portal and selects "edit this page"), so the workflow cannot be created by an editor (who selects an approval group) and assigned to a user. I also don't want to present the user with a drop-down list where they selet the approval group - rules need to be enforced, and anyway those lists get long. I need some sort of logic to select the approval group based on the directory the content they are working with is in, the category/type of the template and/or something else. I was thinking about an XML configuration file to control this but it quickly gets pretty complex and tricky to administer.

What are other companies doing in similar situations and do those solutions work well?