PG - Schroder 30, Smart 8, Pritchard 10
SG - Smart 22, Richardson 26
SF - Brown 35, Nesmith 13
PF - Tatum 36, Parker/G. Williams 12
C - Horford 24, R. Williams 24
Something like that. Kanter will probably play most every night, but will be heavily match-up dependent and no set rotation. Parker and Grant will be heavily match-up dependent on who plays.
I agree with certain key aspects of this. First, I agree that Schroder will be the primary PG for the team with Pritchard as the primary back up. If Dunn is still on the team, he can provide a different defensive look as an alternate back up to Pritchard but not regular minutes. There is really no reason to play Smart at PG at all, but if he is still on the team, maybe 8 minutes, I don't know, I suspect less than that.
As to the PFs though (Parker, GWilliams, Fernando), it is a sorry group but I feel they are going to need to play more than 12 minutes total. Further, I don't see us playing two of Horford, RWilliams, and Kanter at the same time as a way to get a second big on the court, just as this prior post indicates. Last season, GWill had 18 min and Parker 14 min (while with Boston). That is 32 min. Semi played 17 min in addition (I know the box score minutes and the kind of average rotation projection minutes aren't the same but this is still 49 min vs 12 min projected for PFs). It may not be that much this season but I think more than 12 min.
I call it the Hayward line up, that is when we principally used the 1 big approach. That will be used and I think it will be Schroder-Brown-Richardson-Tatum-Horford mostly, but you just can't play the whole game that way or the whole season. Especially when it is resulting in your best player being forced to play out of position.
Parker was playing more minutes (and Grant) because there were so many injuries and not as much guard depth. With better guard depth and with the roster as currently constructed, I don't see Tatum playing anything but PF and Tatum is going to play around 36 mpg (just as he did last year). With Horford and Kanter (in addition to RW), I also don't think Parker or G. Williams will be playing center this year. This is of course discussing a fully healthy roster, which we all know isn't going to happen every game. There will be missed games which will adjust the rotation and minutes.
I do agree with you though, Tatum should not be playing PF much, if at all, but with this roster, he has to. That is why I'd be fine with with a Smart + non-Nesmith young guy for Gallinari or other similar level PF. That would provide a real PF and allow Tatum to play at SF where he should be playing.
So if you traded Smart + G. Williams for Gallinari that would leave the rotation something like this:
PG - Schroder 30, Pritchard/Dunn 18
SG - Brown 29, Richardson 19
SF - Tatum 24, Brown 6, Nesmith 18
PF - Gallinari 24, Tatum 12, Parker 12
C - Horford 24, R. Williams 24
That just makes a lot more sense to me. Clears up some of the log jam in the backcourt and just provides for a better more cohesive roster construction with Tatum playing the majority of his time at SF where he belongs. It also gets more minutes available for Nesmith and Pritchard so the team can really see what they might become. Langford won't play much barring injury or his ability to just take minutes from Richardson, but at least with that sort of trade there is more potential for minutes for him.