Messina is a great basketball mind and he is one the best Euro coaches ever. I think he also can be a legendary college coach since he is a great teacher, not just a manager.
However, he is a hardass indeed and is also stubborn and arrogant. I remember that many CSKA players mentioned in their interviews that they respected him a lot but he was also very, very difficult.
I think hardass coaches can be successful in NBA too but they have to be like Pop or Gomelsky - demanding, sometimes harsh but still be players' coaches. Mike Malone is like that too and I am afraid that Messina is not.