Many teams at all levels already do depending on how they structure play and defensive calling. I was an offensive lineman and linebacker through high school an

Many teams at all levels already do depending on how they structure play and defensive calling. I was an offensive lineman and linebacker through high school and college - our line coach used hand signals for blocking schemes and the OC had 2 different signals he used to indicate which plays should be used from our wrist list. Linebackers communicated changes to defensive backs and safeties with hand signals based on what we saw lineman do or changes we head from the QB.