There is one other thing they could do.
I believe Quintin Ross is on a minimum-level contract, and as such, wouldn't require Washington to take back salary.
So Boston could absorb Boykins via a trade exception, acquire Miller with a slew of expiring contracts, and then in a separate side deal (because he cannot be combined with other players in a deal for another 60 days), trade a draft pick or rights to another player for Ross.
Those combined deals would get Washington under the luxury tax threshold.
Yeah, Ross has a minimum deal so we could give up a heavily protected 2nd round pick to get Washington under the tax.
So it'd be three separate trades to make it work? Weird....
1. Mike Miller for expirings
2. Earl Boykins via trade exception
3. Quinton Ross for a protected 2nd round pick
Well, you could conceivably combine trades 1 and 2 into a single deal. ESPN's trade checker does something to the combined deals, and doesn't show the correct incoming and outgoing salary.
And after double-checking my math, trades 1 and 2 could suffice, depending on who's leaving Boston.
So, it would break down as Boykins and Miller for Scal, Tony Allen, Giddens, and Williams. I imagine Scal would return via a buyout.
It would cash in virtually all our chips, except for Ray Allen.