GuyBanks

You're misunderstanding, I think. They're not better or worse versions of the same thing - They are completely different. 

People have brought up rank systems before. The problem with rank systems is that realistically, the higher rank you are, the less hands on you are and the more you direct others.
 
Also, being limited to certain cars/weapons can already be accomplished by people wanting to play that way.
 
On the idea of not being able to respond to certain calls, the goal has always been to put the player in the shoes of a standard patrol officer, which responds to just about every call someone could possibly think of, whether it's just to do the primary task or to do secondary tasks, such as perimeters. Even rookies show up to those calls because they have to learn how to handle them at some point.
 
Overall, it would be a lot of work put into something unrealistic that would appeal to a very small minority of players. I don't see it happening.