I'd settle for Hayward and a Bill Russell type who can control the boards and plug the middle.
Any of you watch the Simmons interview of Russell on NBA TV yesterday? If you did, you got an idea of Russell's role on those 11 championship teams. There was a lot of video of that era, in the 50s and 60s.
It's clear how they did it. Russ got the rebound, spun in the air and passed it to Cousy (or later, KC Jones). Cousy started the fast break down the court with 3 other guys well spread on the floor. The idea was to beat the defense down the floor and get easy baskets. Layups often, but shots in the key or perimeter, as warranted. In those days, they had great scorers like Cousy, Sharman, Heinsohn; then later Sam Jones, Havlicek.... The combination of Russell on the boards and the fast break transition game proved to be unbeatable.
Simmons comment was it was quite similar to the game the Celtics play right now. They are at their best in the fast break game whenever you see them.
So what's missing? Well, they need another scorer. IT isn't enough. Maybe Hayward would be the other. They also need a Russell like player who can dominate the boards and get the ball to the PG for the fast break. That would not be Horford. But it could be Jordan. He is a similar type of player as Russell, though not as dominant as Russell was. Russ couldn't shoot foul shots either, by the way.
I realize Stevens is a bit young to remember that era, but I think he's hit a wall with the team he currently has. Ainge is more likely to recall that era. The team he played with was not dissimilar from the Russell teams. Another big scorer and an inside big who can get the ball may be a better approach to Hayward and George, though I'm not opposed to that.
You have a rebounder, a PG and three other guys who spread the floor and beat the defense down the court. Two or three passes for the best shot, whether it's a layup, mid range or a 3. That's how they play right now at their best. But they lack the rebounder and the 2nd shooter with IT.