What formation do you play? I can't remember off the top of my head if you can train players to play on either side. By that I mean you go into the training screen, click on the player, teach him to play on the opposite side, job done. I can't remember if you can do that as I've never needed to do it myself.
The other thing you can do, this is what I do, I play my wingers as SS. Because I find when I play them as SMF they come far too deep and actually get in the way (they run backwards towards my LB/RB when they have the ball). So I changed them to SS, pushed them further forward and they stay there now. Ready to counter attack.
The good thing about the SS position is you can play them on the wings in the same way you would an LWF/RWF. But they wont mind which side you stick them on... because as far as they know they're just playing SS.