Richardson going to Chicago would almost certainly make available Keith Bogans (team option) and/or Rasual Butler (free agent). The Celtics were supposedly one of the teams interested in Butler when he was bought out.
Personally, I'd be willing to leave the backup SG role in the hands of some combination of Von Wafer, Delonte West, Avery Bradley, and E'Twuan Moore. If the Celtics got Richardson, I think the team should not pursue bringing back West and Wafer.
I'd rather target bigs and a real backup point guard as the team needs.