I think it would be best to not separate Nazi Germany, Imperial Germany and so on since they're not separate countries, but rather the progression of one. We don't consider Pre-Coup Chile different from Post-Coup Chile and I don't think Nazi Germany should either.
With East Germany however we're dealing with a separate entity that existed alongside 'Germany' and I think it should be split off.
One could make a case for West Germany as a separate flag as well, but they 'won' so they get to count as the 'real' Germany in my book.
“Close” only counts with horseshoes, hand grenades, and tactical nuclear weapons.
That which does not kill me has made a grave tactical error
Source Materiel is always welcome.