Dude! You just completed the Ending the War to End All Wars achievement in Warfare: 1917 and won the Ending the War to End All Wars badge and 15 points!
If you feel the tradeing card system would fail then make "starter" cards untradeable. Then no matter what account they are on they still earned the cards.
 "Dog Eat Dog"){kind=icon}
 "Four Second Frenzy"){kind=icon}
 "Bloons Tower Defense 3"){kind=icon}
 "Warfare: 1917"){kind=icon}
 "Kongai"){kind=icon}