It seems, even within a group with elastic banding on, you can move to the front by doing over your target watts and conversely move to the back by doing lower. To help people focus on attaining as close to their work out wattages perhaps you could be moved up the group depending on how close you are to your target watts. This would reward riders (by showing them up front) for riding the workout as close as possible to intended, which I guess must be the best thing if those who set the workouts know what they are doing (and they certainly seem to).
Not sure how hard to implement that would be