This game has a lot of great features. There are a few bugs, my special teams play disappears when I edit the Playbook. Starting a new game from inside a game causes a freeze. Here are my suggestions:
Game Guide. Another user here has a pretty decent walk through but specific details on how practices work, how the recruiting works, etc
The play editor is buggy. Sometimes a back deep in the backfield wont be visible on the play editor
More than just route options for the play editor. If I am creating zone I should be able to show zones, QB spy, key on flow etc. With this layout you can remove the options for zone, man and blitz and create unique plays. The same goes for offensive plays. It would be cool to put men in motion or have a hand off or option read.
In game play calling. Add features like challenges, replays and double teams or having someone match up with one of their best players.
Stats for plays, so you can see how effective they are and in what situations they are effective.
Recruiting management. Could be computer assisted but still have simple inputs such as go after this recruit aggressively by allocating so many points to this recruit until they are signed or say no.
Assigning practice screens could have attributes to show what a player needs. Do they need weight lifting or track practice?
Input on allocating funds for campus. Either on equipment, facilities, stadiums etc.
Fake play designs.
More random events. Usually in sim games its done via a newspaper function. Why change whats not broken. Maybe post game interviews etc.
You get a salary but what do you spend the money on?
I think this covers my initial assessment and suggestion.