He's the new Rasheed Wallace, IMO. Extremely talented, his reputation hurts him when it comes to calls on anything, he can lose his temper at any time, etc. I don't think you want him to be your franchise player even though it is debatable that he has the talent to be. Remember the least controversial year he had was his one year in college when he was not the best player on his team. Maybe if he could have a similar situation in the NBA it would help him.
Sheed has had an outstanding career too, but I don't think he ever became the franchise player anyone wanted or expected. And honestly, some of his best years were when he went to Detroit and was arguably their 2nd or 3rd best player. He had some better numbers in Portland, but after 2000 that team underachieved and then the whole Jail Blazers mess began.
Cousins probably would be best off as a 2nd option on a team with a playmaking PG. I understand why Sacramento doesn't want to trade him away, especially since it would be difficult to get anywhere close to as much talent as they would be shipping out. But ultimately, I do not see him recognizing his full potential until he is on a different team as the #2 or even #3 option, similar to how Sheed was.