Flashman, can you be a little more specific about what you mean by “a nation is defeated?” Does that mean all of the nation’s pieces are immediately removed from the map when it loses its last production center? If not, are there any practical consequences to being “defeated” other than not being able to produce new units? And by “nation,” do you have in mind something like “France,” or more like “the Allies?”
If you treat production centers as victory cities, then how many victory cities do you think each side should have to control in order to win? Would you have any victory cities that are not also production centers?
Finally, would you agree that banning the creation of new factories takes some of the variety and surprise out of the game? Off the top of my head, it seems like Japan is more or less required to try to conquer India (since Japan can no longer build a factory in Manchuria or Kazakh), and the USA is more or less required to try to conquer Italy or Tokyo (since the USA can no longer build a factory in France, NW Europe, or Norway). I would also be sad to lose the option of having the UK build a factory in South Africa, having the USA build a factory in Sinkiang, having the UK (or Germans!) build a factory in Egypt, having Japan build a factory in Alaska, and having the USA build a factory in Borneo or the Philippines. No one of these options is really part of ‘orthodox’ play, but collectively they spice the game up quite a bit, and often players will adjust their moves to make sure that these builds don’t become optimal. For example, the US might leave a significant garrison, including a tank and a fighter, in Western USA / Western Canada to guard against a Japanese Alaskan factory, but if Japan can’t build in Alaska, then the USA can make do with a much smaller, cheaper, more passive defense of the homeland.