My stab at a Cs for #4 trade
Suns get Rozier, Parsons, 2019 Grizz 1st
Grizz get TJ Warren, #16 (from suns), 2019 Sac 1st, #27 (from Cs), Marcus Morris
Cs get #4
Why
Suns land Rozier to start along side Booker, Jackson, Bender and Ayton and a potential loto pick next year. If they plan on developing youth and not diving into FA market then Parsons deal isnt going to make a huge difference.
Grizz, They bring in two players in Morris and Warren who will help them win next season. The 19 Sac pick should be upper lottery. Adding the 16 and 27 to go along with the 32 they already have should be able to move them back up to the 10-12 range if they have a late lottery player they want. (Maybe Lonnie Walker?)
Celtics, At #4 they can get the big man of the future in Jackson, Bamba or Carter. This also eliminates the need to resign Baynes and that coupled with moving Morris opens up space under the luxury tax to retain Smart.