I play with wingers too, I like to use AML/R. First off, I don't care much for ratings of ST and AML/R, they have one job, and that's to score. And that's where I select my players on when I buy a AML/R or ST. I've found that speed is their (AML/R) greatest asset so assign most points to physical and mental.

Furthermore like skidz said, if you play with AML/R or red arrow your ML/R, you need back up behind you so I always use a DR/L or DMR/L sometimes as I like to butterfly sometimes. Like you I always use focus passing on mixed. I think MC is one of the most critical positions in the game and I don't want them to get bad or avg ratings as that might have a negative impact on the result. I prefer to focus attack with arrows on wingers and sometimes an MC or DMC.