I just see Bradley as better suited to being a starter, mainly because he can't play the point, so would be horrible in the role of combo guard off the bench. I am open to an upgrade, but I would be bitterly opposed to replacing him with a guy who can score 20ppg but doesn't play defense, especially if he is a bad three-point shooter. I just don't think that sort of player would fit on a Stevens-coached team.
If the Celtics add Asik, I would like them to add a sixth man SF/SG who can score some and defend the bigger SGs who I think Bradley can defend, but who will cause him to foul out. The alternative would be to acquire a SF who would push Green into a sixth man role where he backs up SF and plays some minutes at PF and SG.