The Celtics (other than an embarrassment of riches in picks) have an embarrassment of riches in good players. They have Crowder, Bradley, Smart and KO who are all playing below market value. In this scenario, where you want to make a big move and sign a guy like Hayward, they can't realistically keep all their good players. And I'm a firm believer that the C's have to make a splash.
If I had to identify the core of our team (aka near untradeables), I'm going with IT-Horford-Brown and eventually Fultz. As "cold" as it seems, I'm open to moving anybody else if it means improving our team with a Hayward or Butler-type acquisition.
Among Bradley/Crowder/Smart, the one I'm most inclined to keep is Smart. He'll probably make the least, be most amenable to taking the least, while still embodying Celtics culture. He's not as talented as Bradley/Crowder, but then again, those 2 guys likely aren't as talented as a guy like Butler/George/Hayward or eventually, Fultz/Brown.