MAVS NEWS:

[F Gump]

Literally the only trade I can think of that will bring anything back to Dallas for Klay is Kuminga. That´s cause GS loves Klay and hates Kuminga. 

I like Klay. I am not a fan of Kuminga. But if I'm the Mavs, I would certainly entertain Klay, for Kuminga and a pick. 

The tricky part is that both teams are A2 hard capped, close to A2, neither can take back more salary than they send (within 100K), and both have full rosters. So the salary match would be hard because it has to be almost exact.

I see one way to make such a trade fit the rules. It would utilize existing TE. 
1 GS waives a player (or trades a player for a pick, as a 3rd team in the trade) to open up a roster slot. The Mavs could not take the player themselves because of the A2 hard cap on them. 
2 Then ...
Kuminga and a pick 
FOR
Klay and Hardy