My guess is that lag would prevent this from working. I've seen times when we've had 20 people all in quasi-formation. Inevitably, though we're all flying at the same engine settings, same altitude, etc. Somebody is moving a little faster or slower and doing so in a slightly jumpy manner. That jumpiness is the lag associated with the system predicting where they are going to be and then getting an update that's elsewhere. Its small, but my guess is that this would make this feature difficult to implement.