True, there is really no way to pick the best lineup unless some people with great football knowledge watch all games and come out with a objective XI.
You're right about the wingbacks, but does that really matter in a yearly XI? It's not like they will play together, it's just picking the best performers and keeping it close to what a football formation would be. Remember seeing 3-3-4 lineups with Marcelo and DA in the back 3, or 3 AMs/wingers in the midfield trio...