I don't think Thomas and Turner should see the floor together. For the purpose of the rotation, they should be a platoon. Those are the primary ball-handlers for the team until Smart and Rozier develop further. Neither of them is really worth having on the floor (and putting up with their weaknesses) if they are playing off the ball.
Thomas is difficult to put in the starting lineup because his size is a liability; tougher to score against generally bigger, more talented starting guards, and tougher to defend against the same.