during the trailer there is mention of a battle of ideologies. In that pic of Big Boss he's split down the middle with the United States flag on one side and the U.S.S.R. flag on the other. That's gotta represent some sort of conflict within.
https://www.konamijpn.com/products/mg...ouflage_17.gif
A mercenary isn't really on either side of the fence to begin with..so turning bad isn't such a tragic fall from grace as someone who was once good and became bad. Still it's going to be interesting how Kojima presents Big Boss to the fans.