I would say that the guys that the things that shouldn't be traded without a really crazy offer are: any of the Brooklyn picks, Marcus Smart, IT4, Bradley, RJ Hunter, KO, Jordan Mickey and Crowder.
The things that are decent assets and should be used to grab players in a trade if possible are: any of our picks, the Philly 2nd rounder which will be 1st overall, the Dallas pick, the Minny pick(s), Sullinger, David Lee's expiring, Amir Johnson's contract which is specifically designed to be traded, James Young, Terry Rozier and Memphis' 2018 first rounder (most likely we are getting that or their 2019 pick).
Things that are bad/clogging roster spaces that we should get rid of: any of our second rounders, Zeller, Jerebko, Miami's second rounder in 2016, Cleveland's 2017 second rounder, LA Clippers' 2nd rounder, Detroit's 2019 second rounder, Miami's 2020 second rounder and Marcus Thorton 2.
So if we can use things from the 2nd group and the 3rd group to grab someone like Noel we should do it, but let's not use Group 1 assets quite yet.