Has it outlived its usefulness?
I can completely understand why you'd want to have a system with baseline prestige in place during the inaugural seasons of a new world. But after 50 or so seasons, couldn't you now use a weighted team history to formulate prestige?
The system in place is too restrictive imo. Make the process of obtaining an A+ prestige very easy for certain team, very difficult for others ... but never impossible. As a 'what-if' game, there shouldn't be hard barriers on what a coach can or cannot achieve.