Here's a trade that kinda makes sense for all 4:
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I know Nash said they're not trading Harden now, but if Harden let them know he's leaving at the end of the season, then I think they'd jump at this haul, especially as Simmons would be a pretty much perfect fit in Brooklyn.
Also (according to the Bill Simmons podcast I listened to - not an experience I recommend) the Nets want shooting help, in part because Joe Harris's situation is so uncertain, and could use Fournier.
Knicks get CJ, whom they're supposed to want. We avoid getting their terrible contracts and actually shave $12M off our cap, making the real decision makers very happy. I doubt this trade makes anyone on this board happy, but having seen CJ's negative effect on the team since he came back, think of it as addition by subtraction.