No pipe dreams like Tim Duncan or Tyson Chandler. So these would be some moves I would like to see them make:
1) Get Chris Johnson Back
Even though he's skinny, he's a big young body who has potential to be a rotation player. Plus he's a decent shot blocker and is only 25.
2) Resign Delonte West, Jeff Green, and Von Wafer
Delonte West and Jeff Green are obvious resigns, but I put Wafer here because he's athletic and would be better than bringing in a new third string guard. He should be resigned, but only for the minimum
3) Draft either Jeremy Tyler or Nikola Vucevic with the 25th pick, and Jeremiah Rivers with the 55th pick
If available, the Celtics should nab Jeremy Tyler. Like Bradley last year, he was a top prospect in high school but faded away in his college, or overseas, career the next year. Most people forget about what he was capable of and could be capable of with the right teacher. If he's not available, they should take Nikola Vucevic, who could be a young center to play minutes in the regular season.
Jeremiah Rivers would be a good pickup for the 55th pick, who could take minutes away from Ray Allen in the regular season and would be a fan favorite.
I didn't discuss free agent targets in this, but if you have any ideas I would love to hear them!