Some of this depends on how ready Zizic is. If he can give the C's 25 productive minutes a night at center, that means Horford can play some PF.
And as the league moves more and more toward small ball, there will be more and more opportunities for Brown, Crowder, Tatum, and Hayward (if he comes) to play positionless around the 2-3-4 spots.
With Gibson in Minnesota, there really isn't anyone on the FA market that I think means much for the C's and the trade market I just don't know. Could Aaron Gordon be gotten? If the Lakers are trying to clear space for next summer, does Larry Nance hold any interest?