I think such resignation is part of the game, and should be taken into consideration by military-heavy players. Otherwise, a military weak player can also really throw the game off balance, because military players gain too much of an advantage. So if a single player is far behind on military, the other players would be forced to go full military. And even in that case, culture is limited, so it would have been distributed unevenly (who attacks first would get a huge advantage).
