I was very concerned about the Center position too. I thought it would be great if we can get Kwame Brown. But then I realized if Kwame Brown was our best option we have to change our plan. I think we can get away without a legit center.
1) I couldn't name 5 centers in the league that can score 20 points per game against Glen Davis or Jermaine O'Neal.
2) The Big 4 with Glen Davis was the best starting 5 line-up in the NBA last season. They played a significant amount of minutes and were better than the line-up with Shaq and Perkins.
3) The power forward spot is loaded Boozer, Bosh, Stoudemire, Brand, Josh Smith/Al Horford, Gasol, Dirk, Griffin, Duncan, Love etc.
4) The league is changing to favor speed and athleticism, over size and banging.
5) A lot of teams have success with undersized strong Centers. Blair, Hayes, Davis, Okafor, Bass(after the Gortat trade) and Landry(Rockets) have all played the Center position with success.
With these thoughts in mind, I would build our team like this:
Point Guards
1) Rajon Rondo
2) Delonte West
3) Avery Bradley
4) E'Twaun Moore
Shooting Guards
1) Ray Allen
2) Josh Howard (If too $$, Gilbert Brown/Sasha Pavlovic)
3) Von Wafer
Small Forwards
1) Paul Pierce
2) Jeff Green
3) Marquis Daniels
Power Forward
1) Kevin Garnett
2) Carl Landry (our main F.A. target)
3) JaJuan Johnson
Center
1) Glen Davis
2) Jermaine O'Neal
Jermaine O'Neal is injury prone, but Landry can play some Center. Also we can have small lineups with Jeff Green at 4 and KG at 5. JaJuan Johnson can play some minutes at center too (His build and reach is similar to Noah.) A little luck avoiding injuries and I can see this team bring home 18.