Send them Sheed and a check for Beasley and 18.
Doesn't help them clear cap space for free agents, unfortunately. They'd need to trade for a contract that is not fully guaranteed.
They would need Wallace to say he was retiring, 100%. Then, it works for them.
And giving up the last two years on his deal.
He can certainly say, "I'm retiring, but I'm still going to take the money owed to me on my contract."
It sure seems like that happens, but I'm pretty sure that players have to make it official with retirement players or they can be held to their contracts. If they retire, they forego any outstanding pay, and it comes off the cap. Asking for a buyout is not the same as retiring, but owners perhaps tend to make some sort of payout to avoid any potential mess.