(click on image to enlarge)

PG: Smart
SG: Beal
SF: Brown
PF: Tatum
C: Timelord
It's an ''ideal offseason'' scenario, hence I'm assuming Beal forces his way to Boston to team up with Tatum. Either he opts in (like CP3 did in 2017 prior to his Rockets trade) or he hits free agency and the Wiz sign-and-trade him to the C's. I'm too lazy to put down the numbers, but I'm pretty confident we can stay below the apron.
I don't think that is near enough for Beal and I'd want to keep Horford in that scenario. I'd honestly rather just trade both Smart and White than Horford. And I know that sounds weird, but there is only 1 ball and Beal would be the starting PG, so there are a lot less minutes for either Smart or White in that scenario
Smart, White, Nesmith, 23 1st, 25 1st (top 4)
for
Beal, Smith
So post-trade contracts
PG - Beal, Pritchard, Smith
SG - Brown
SF - Tatum, Hauser, Stauskas
PF - Horford, Grant, Morgan, Fitts
C - Rob, Theis
Still have the TMLE and all the TPE's to add to the team (though basically no 1st's to trade). However, I'd be open to a salary dump. Like say Miami wants to get out of Duncan Robinson, I'd be open to him coming into the Fournier TPE for a 2nd round pick. Adding him as a shooting wing off the bench would fill a real need. With the Mavs getting Wood, maybe they'd be open to dumping Kleber (he fits into the Thompson TPE).
So that would be a pretty sweet team
PG - Beal, Pritchard, Smith
SG - Brown, Robinson
SF - Tatum, Hauser, Stauskas
PF - Horford, Grant, Kleber, Morgan, Fitts
C - Rob, Theis
Now that is a real contender. Much better offense and while the defense is hurt some, it still have plenty of guys capable of getting defensive stops when needed.