They wern't winning championships with a pick and roll, run and gun offense. They won them with a triangle scheme which keeps your big men routinely close to the basket instead of spreading them out.
And they are a slow starting five. You're way off base there. They are definitely one of the slowest teams in the league. They don't have Shannon Brown any more. They need outside shooting help and order to thrive in that offensive system.
You talked about their lack of shooters. I pointed out they won championships without shooters. That has always been a problem for them.
The triangle is more about ball movement and spacing than keeping bigs close to the basket, although it is more of an inside out game.
I'm not convinced D'Antoni can win championships and I thought Phil was the right choice, but I think you're overstating how the players will adapt to his system.
Regarding team speed, I disagree. Which 5 in the NBA runs better than Howard? Pau will not be on anyone's track and field team, but he runs well for a 4. Metta is not slow. Kobe is not slow. Neither is Nash. Nash actually has great basketball speed (not sure if is such a thing, like football speed).