"A regular slot, but highlighting a different theme, group, subgenre, or history each time.
Maybe one series on the song collectors, with examples of songs they collected, one series on traditional singers, with their songs, one on the development over time of musical styles, and so on.
That would also allow new or unknown singers/performers to be used in the various examples."

yes pavane, and probably these ideas have been submitted and rejected. The beeb get a lot of submissions for each slot. I've been approached by a couple of companies to present ideas for filling an alloted slot. Only one has ever been accepted by the BBC. The others were not considered broad enough, or contained enough "celebrity" names for national broadcast.