What's the most you give up for Cousins?
Here's what I offer at most:
http://www.espn.com/nba/tradeMachine?tradeId=gt4shg9Sacramento: Zeller, Brown, Olynyk, Rozier, 2017 Brooklyn pick, 2019 Memphis pick
Boston: Boogie, Collison
That leaves you with the following rotation:
PG: IT, Collison (who is an excellent two-way guard off the bench)
SG: Bradley, Smart
SF: Crowder, Green
PF: Horford, JJ
C: Cousins, Amir
That's a really solid 10-man rotation for the rest of the season to win games, possibly overtake the Cavs at the number one spot, and get rest to guys who need it for the playoffs. Then you have a really strong 8-9 man rotation of IT, Bradley, Crowder, Horford, Cousins, Collison, and JJ/Amir for the playoffs.
EDIT: Or Amir, Zeller, Brown, Rozier, the 2017 Brooklyn pick, and the 2019 Memphis pick for Boogie, Collison, and Casspi would also be a good deal for us.