The best thing going for us in this free agency period is the prospect of addition by subtraction with Big Baby. With Perk, JO and Shaq out for so much of last year, Baby was more 5th than 6th man.
If JO or Jeff Green can combine to fill those minutes, we're already a better team.
As for addition by addition, there are certainly a lot of intriguing possibilities, though the Ainge's desire for 2012 cap space could tie our hand a bit.
A key domino to look out for is Jeff Green's fate. If we sign him to a multi-year deal, we'll have little to no flexibility to sign another multi-year guy without spoiling our 2012 cap space (if the cap ends up around $55 mil, Pierce, Rondo and our draft picks will occupy about $30 mil of that; add on Jeff Green at around $7 mil and you can't really go further without losing a max slot). I think resigning him would also minimize the need for a back-up 4, as Green would likely see regular minutes there.
If we let Green walk, or sign him to his QO (or sign & trade him for someone on a one year deal), then I see Ainge being much more willing to offer a multi-year MLE.
In the first scenario (Green resigned for multiple years), I see Ainge splitting the MLE up and offering 1 year deals to journeymen bigs like Kwame Brown, Chuck Hayes or Chris Wilcox, trying to retain Delonte for the LLE, and then scouring for vet min guys to flesh out the wings spots behind Jeff Green.
If it's the second scenario (Green gone or on a 1 year - the most likely scenario, IMHO), then there are a lot of interesting guys Ainge could throw multiple-year offers at. There are intriguing restricted free agents like Wilson Chandler, Arron Aflalo and Jonas Jerebko. A lot of skilled wings: VC, Tayshaun Prince, JR Smith, Mike Dunleavy. Then of course the bigs: K-Mart, Landry, Humphries, Dalembert (probably out of our price range, but what the hey)... Any one of these guys could be the missing piece for a final title run.