Wcs and randle... first we must see what brown and tatum can do
There are several possible combinations but I like this one.  Any expectation has to consider the realities of our available salary cap which I think this one does.  I prefer signing players over trading (say for Capela).
Randle has improved a lot.  Randle can give us something between what Morris did and what Horford did.  Randle is not Horford, at least not yet, but I feel he is on that track.  Randle would be smart to model his game after Horford.  WCS is more in the mold of Baynes but better.  More of a banger with limited scoring.
So if Randle can be Horford-like, and WCS can be Baynes-plus, we should be in pretty good shape.  Not a bad way to spend our cap space in my opinion (if it works out that way).  So then we could debate what is better, Horford+Baynes or Randle+WSC.  I actually think we might come out slightly ahead in the long run.
PG     Smart
Wing  Brown
Wing  Tatum
Big     Randle
Big     Cauley-Stein
Rozier      (PG)
Hayward  (Wing)
Ojeleye    (Swing
Williams   (Big)
Randle reminds me a little of a young Karl Malone when looking at his combination of physical strength and sthleticism at the PF spot. 
I am intrigued by the idea of adding an athletic big like that to an already young and athletic core of Brown, Tatum and possibly Rozier.  That could be one hell of a fast break team.  
He also provides Boston with a presence in the paint, which I actually think is a good thing, not a bad thing.  He's a strong rebounder and skilled post scorer who draws fouls at a high rate - something Boston desperately needs.  
Factor in that he actually shot a half decent 34% from three last year, and you also have an indication that he has potential to be able to stretch the floor as well.  
As a 24 year old his age also lines up nicely with out existing young core.  
He's not perfect, but he's a good player who could be on the verge of further breaking out, I'd be willing to jump on board.