I don't think Dooling can be a key piece to this. I am not sure so I'd want some confirmation, but my understanding is that a player used in a sign and trade has to be signed for three years. So Houston would have to WANT Dooling.
That means to me the trade pieces are going to have to be Johnson, Moore, Williams and picks. Moore and Williams have non-guaranteed contracts and so could be waived by Houston (Moore has to be waived by the end of the Vegas summer league, Williams by August 1, or the contracts become guaranteed). 150% of that salary value plus $100,000 (the amount Boston could bring back in a trade) is about $4.25 million.
For what it's worth, I'd combine next year's first rounder with that offer to get Lee on a three year, $12-14 million deal. Signs point to next year being a bad draft. Yes, there could absolutely be a good player who falls, but in bad drafts, those late first rounders come cheaper so one can be acquired. Plus Boston has Charlotte's second rounder next year which won't be too far from a first rounder. It's a worthwhile sacrifice with what we'd have from this trade. Rondo, Bradley, Terry, and Lee is a very good backcourt. Pierce, Bass, Green, Sullinger is a solid forward rotation, Garnett, Melo, Stiemsma at center. Four spots remaining for potential add-ons like Joseph, Dooling, Pietrus, Hollins, Wilcox, etc.
Is Lee an adequate replacement for Ray? No. But start comparing the team that made it to Game 7 of the East Finals with what we'd have. Is Bradley, Terry, Lee and Green an upgrade on Ray and Pietrus? Yes, by a significant margin. Anything Sullinger or Melo adds becomes bonus. This team would be better than last year's team provided KG remains healthy and Rondo can maintain his level of play when it counts.