I see your point about
Margaret Georgia. My main critique of it is not that it sounds like a city, but that the gret-Geor flow is a bit harsh.
Georgia would be after my father-in-law,
George, though, so it would get double points for family names.
Margaret Elena is nice! As are
Margaret Alice,
Margaret Eleanor, and
Margaret Cecily.
Margaret Cecilia could be nice too. I know DH and I both like
Cecilia.