We had debates on this at the time, and I think the general thought was Ainge would have taken Bridges. This is my memory of it. Miles Bridges would obviously have been a terrible result, but pairing Mikal and Smart would have been cool.
Mikal is who he would have taken, though who know what happens with Miles if he is in Boston and not Charlotte.
I do also think there is a chance he would have taken Sexton. Remember this was a full year after we made the trade so Thomas wouldn't have been on the team, and Sexton did fit the profile of guys Ainge liked (though we did have Rozier still at that time).
Either way, Mikal, SGA, or Sexton would have been a much better result.
As I've consistently maintained, it wasn't the trade for Kyrie that was the problem, it was Ainge's inability to pull the trigger on the necessary follow-up trade. Boston probably has a title if he would have just pulled the trigger on Leonard or Davis, even with the risk they just left in free agency. And who knows what would have happened in free agency after that.
Ainge just never fully committed to win now or build for the future. That was the problem.