It seems like you want franchise progression to mimic what will happen in the NFL in the future. I'm sorry, but you aren't going to get that with any offline franchise. Like someone said, once you start your franchise, real life is out the window. There are too many variables that determine how your franchise is going to play out. In one franchise, my favorite rookie may have a career ending injury, in real life he may have a HOF career. The devs have to make an educated guess at how a player's career will play out. They won't be perfect which is why I do agree that the user should be able to change a player's potential.
If a player has a breakout year in real life, their abilities will be re-evaluated by the dev team. But that should not be confused with progression within your franchise.