First, there should be linking between contacts and Groups like there is for contacts and Companies. Makes no sense why one is done and the other is not. Sage should make the linking more bi-directional with a well thought out process of how it can be done.
For example, the contact should be able to "push" it's info field-by-field if possible. Maybe a right-click context menu to do it? Maybe a form that opens up and asks the user what to do. Plenty of ideas to get it done. It would be nice if it could be on a field-by-field option.