Well KG and Pierce probably play 3-5 more years if they are playing with Dwight and winning titles.
I'd do something like Rondo & some some picks for Dwight. But otherwise salaries won't match until recently signed guys become trade-able (would have to send Rondo, JJJ, Moore, Williams, and S&T Dooling.)
SG becomes a challenge in that situation, as there would be no hope of adding anyone but a BAE guy. If you could get Lee for the BAE you'd be in business.
AB, Lee, Pierce, KG, Dwight
with Terry, Green, Bass & Sully as your 9 man rotation. KG would shift to Center when Dwight was out, and you'd limit the amount of time you had a two PF lineup (Sully at C and Bass at PF.) Melo, a wing, and a PG get you to your 12 man rotation.
Alternatively if that trade happened today - maybe Ray Allen decided to resign with BOS, since his relationship with Rondo is a non-issue and he'd be assured a starting job, and the C's would be better positioned for a championship run.
AB, Ray, Pierce, KG, Dwight - offense would run through KG and Pierce a lot, but with Terry off the bench, I think that's OK.