Uneducated guess here, but I think you'd have to largely gut this team to trade for Cousins.
Are you willing to add Cousins if it costs you Smart, Bradley, Crowder, BK #1, Dallas #1, 2 2nds and a Young/Mickey type?
I think the asking price would be in that range.
Stevens would be great for Cousins, but so would Crowder and the other good glue guys we wouldn't want to give up.
If we strike it big on one or two picks this year, sign a quality FA and package lower picks and lesser players to adjust the rest of the roster, we will retain the tremendous depth and have loads of upside and continued flexibility.