I'm not saying a true butt crevasse, but I am saying someone like Rizzi who the players loved, but is clearly a guy that will get in a player's face. Even Payton did that and the players loved him. It can get old if done too much, but an assistant can get away with it more than a HC because the HC can come over and be like yeah that was over the top, but we all just want to see you become a better player, correct the mistakes, etc.
But, sure, there is more than one way to do this so maybe you don't need that as much as you just need a guy that demands perfection and won't accept anything less.