Leaving aside my agree to the opinions against the idea (Craftsman, King_max, SpartanBG, etc), I must note I played in games who makes similar packs (let's call those games "eR") and they become really disastrous for free players: it's practically impossible to enjoy the game WITHOUT buying those packs and even the (few) community will only value you by those packs, not by your strength or skill. Free players becomes utterly useless and there isn't worst sensation than to be a useless player in a game.
Besides, those proposals are pretty unrealistic with the WWI topic. That war represented the zenit of technological and psychological warfare. People believing the war would be won by showing more courage than the enemy were mowed down by machine guns in No Man's Land, and while the war went longer and longer, more and more people was looking for ways to avoid recruitment or to defect from the frontline, let's not mention the futility of fortress against modern artillery. or buildings destroyed once and again during the fight. Your ideas, hence, are totally unfit with the representation of "The War to end all Wars."
Edit to add: Your first idea sounds me similar to this. And well... if Wonder Woman would have been fighting with the Allies in the Western Front, that war wouldn't have extended for four years.