Isaiah Thomas.
Thomas-Fultz back court with Fultz playing SG more (he's more than capable - even he believes he can).
Rozier as a solid bench option.
I'll admit idk who stays out of Bradley/Smart (real tough call), but either one has potential to be a great 6th/7th man for a contending team (aka US starting in the next 2-3 years). Maybe they can keep both though with Rozier being traded for another piece/need
I'm REALLY hoping Isaiah can agree to some "Westbrook-like extension" (around 3/87M, option 3rd year), and I don't really think, EVEN THOUGH HE DESERVES IT, any other team would give him a 4-year max, and the C's hesitate on the 5-year supermax as well.
A lot also depends on how Fultz's defense progresses. If he is average (and slightly better than Harden - his ceiling player on most mocks), that's a stud and it works out very well!