I would play make shift teams against Tonga and USA but not Argentina but I get why people would want to rest some for the France game. If England make it to the final that's Argentina, France, Aus or Wales, New Zealand and 1 of Ireland or South Africa. 5 tough games against the best teams all in a row in a short space of time with little rest. In groups most teams have that 1 tough game and can rest the squad during the group stage. England from game 3 in groups have it tough.