This should already be possible with an alternate world map view where it's:
empty by default
clicking sets the lat/lon coords and loads the polity shapes that overlap those coords across time
also loads the basemap current border shapes that overlap either that point or any of the polity shapes
sets zoom to that point
This could become the default world map view as it would be much quicker to load. There could then be an "all polities" toggle that allows you to view the current world map once that becomes available.
Could also use GADM shapes as an alternative to a lat/lon point as the thing to compute the overlap with. This would mean you could select a province or small administrative area and see what polity it was in historically.
Could we copy the approach used by:
This should already be possible with an alternate world map view where it's:
This could become the default world map view as it would be much quicker to load. There could then be an "all polities" toggle that allows you to view the current world map once that becomes available.
Could also use GADM shapes as an alternative to a lat/lon point as the thing to compute the overlap with. This would mean you could select a province or small administrative area and see what polity it was in historically.