Below is my depth chart. Couple of points, Nesmith is a rookie and is 3rd string until he proves otherwise. I wish we had a decent PF or Swing to start in place of Smart (and slide Brown and Tatum up to SG and SF) but we don't so we have to play Tatum out of position. And last, our biggest weakness is the Wing/SF off the bench. I don't buy that GWilliams can be that (he may be second team big over RWilliams though) or Ojeleye. I don't give that to a rookie, so we are stuck with Javonte Green.
Not every player is going to fit into a roster box, I understand. Overall, this is still pretty good. Some holes to fill or upgrade but that is true of most any team. Priority 1 for me is to find that veteran wing/forward who can play off the bench for us (not Lou Williams). Priority 2 would be to find a starting level Big (probably PF) or Swing that can allow us to play a 2-big line up without giving up too much skill.
Walker Teague Pritchard
Smart Langford Edwards
Brown Green Nesmith
Tatum Theis GWilliams
Thompson RWilliams Ojeleye
I don't like playing your best players (slightly) out of position. You're creating two problems instead of one.
For me there are two players who are unquestionable starters: Brown SG and Tatum SF. The third one, when healthy is Walker PG.
So we have: Walker - Brown - Tatum - ? - ?. And then you're going to fill the other two positions based on the roster and balance.
Rest of the roster consists of definite rotation players in Smart/Theis/Thompson, rotation/bench players in Teague/G.Williams/R.Williams/Nesmith and bench players Langford/Pritchard/Ojeleye/Edwards (and are they bringing back Javonte Green?).
Then Smart becomes 6th man automatically. At least one of Theis and Thompson can start, logically Theis starts until being outplayed. Other guards and small wings can be filled in as bench players as well. So we have: Walker - Brown - Tatum - ? - Theis, and bench Teague(Pritchard) - Smart - Nesmith(Langford) - (Ojeleye) - ?.
We have one position (PF) to fill and 3 options left: Thompson/G.Williams/R.Williams. Since Thompson is a higher category player and R.Williams isn't necessarily a better fit, also R.Williams goes to the bench. Thus it's between Thompson and Grant Williams to start. Since Thompson is also starting to shoot the three, I wouldn't bench him for Grant Williams (with 3 starters being very good from outside it isn't an absolute necessity anyway).
That makes the rotation (for the start of the season and assuming Walker healthy, one roster spot open) complete:Starting: Kemba Walker / Jaylen Brown / Jayson Tatum / Tristan Thompson / Daniel Theis
Rotation: Jeff Teague / Marcus Smart / Aaron Nesmith / Grant Williams / Robert Williams
Bench: Payton Pritchard / Carsen Edwards (G-league) / Romeo Langford (injured) / Semi Ojeleye