There is some difference between slow playing and slow rolling, I have been in some situations where I have made the "Nuts" on the River and depending on my position in the betting order, I have had to think how much I should bet in order to extract more chips from my opponents, Too big and they could run away and too little will not give much in return, So obviously if someone shoves All-in I am going to take some time to think if others are still involved in the hand, But if we were the last two playing in the hand, My chips would be in faster than the other player who declares all-in.
There is nothing clever about winning a hand with the "Nuts" and tanking in order to drag it out, all you are doing is prolonging the other players agony in defeat which is never Funny or Clever. It is a sure way to lose Respect and Friendship.
Penalties would be a way to stop such behaviour, but nothing short of a forced sit out for a full rotation of the table would do any damage to an offending player, Something similar to the Shark Tank games I have seen on TV.