How about a special jersey for group ride leaders? I realize this might require a secret code to be shared only with official group ride leaders so as to not have more than one per ride, but that seems easy to do. Additionally, since it’s tough for people to find the ride leader in a large group, how about putting a floating indicator above his head? As far as I can recall, there was a floating indicator used in the flyer detection when it was first implemented, so that seems easy too. Perhaps some kind of shining star icon or something sufficiently rideleaderish.
You could also put a widget on the ride leader’s name in the list.