It is going to come down to the following
Is KO resigned?
If YES then AB or Smart gets traded (or maybe IT and Jackson) and Yabu is left in China for another year
If NO then Rozier and Jackson have to be traded and Yabu stays in China
After that I think DA makes it Brads problem for the first half of the season.
For the sake of argument lets say that Hayward lets it be know that he plans to sign with Boston. The Cs would then put in motion loosing KO and trading Rozier for a future pick or a draft and stash. Other minor moves like waiving Zeller and Mickey then letting Amir, JJ and Green walk will need to occur. After drafting Fultz and at least 1 2nd round pick who may make the team. The Cs then sign Hayward and Zizic and are left with the following roster.
PG IT, Fultz, Smart
SG AB
SF Hayward, Crowder, Brown
PF
C Horford, Zizic
I am not a cap expert but I believe at this point min salary players can be added to the roster. In the early second round I would like to see the Cs target a big man who has potential to actually play in the near future Ex Swanigan (DX #40 or Bell (DX #33). With one of the late 2nd round picks the Cs could give a productive old college player a shot at making the team Ex F Mason (DX #48), Thornwell (DX #56), or Sterling Brown DX #59 For FA maybe Amir and Green can be sold on resigning for a min deal? Nader would be a nice signing out of the D-league (now G-league).
That would leave the roster as the following
PG IT, Fultz, Smart, Mason (2nd rd pick)
SG AB, Green (min FA)
SF Hayward, Crowder, Brown, Nader (FA)
PF Swanigan (2nd rd pick)
C Horford, Zizic, Amir (min FA)
That is a 14 man roster with room to add a vet PF at the end of FA and 2 two way contracts
As for the rotation BS may have some issues taken care of for him if IT needs hip surgery. This could keep him out till Dec and allow BS to start out with the following Rotation.
PG Smart/Fultz
SG AB
SF Hayward
PF Crowder
C Horford
6th Fultz/Smart
7th Brown
8th Zizic
9th Amir ?
That rotation would allow everyone to play adequate minutes to start the year and allow DA to figure out the future of the back-court.
If IT is healthy to start the season then Smart, Fultz and Brown are all left to battle over the roughly 45-48 minutes backing up the 1-3 positions.
Ultimately the next trade deadline would set the stage for this rosters path with either IT, AB, or Smart likely traded at this point. I personally think if Fultz shows enough to make DA believe he can be a 20+ppg lead guard that IT is moved at the deadline rather then signing him to a huge contract.