I'd like more insight on this as well but this seems to be pretty dope with the testing I did (simmed/analzyed a season week to week). Everyone starts each season with a 3 confidence. As they play each week their confidence could change from game to game depending if they played good or bad and go up or down accordingly. A 1 or 2 confidence means the ratings are changing towards the negative and a 4 or 5 means towards the positive (this works even when simming games and you'll see the stats reflect this. Dope). The higher the constistency the smaller the window of the rating change. The lower the consistency the bigger the fluctuation (reference the EA blog on this). So a 1 consistency and a 5 confidence will mean the ratings will greatly change on the positive side (overachieve). A 5 consistency will have very minimal rating changes even if a 1 confidence (so the EA blog recommended building a consistent team to avoid the great rating fluctuations when vying for that last playoff spot in wk 17). What I'm not clear on is if the consistency rating can ever change....
I also started to play a game and the DPP showed me all the changes I mentioned above on the pause screen right after the coin toss. Nice. I *think* the player traits change with the DPP...and adjust the C & C above...
Roles are reassigned at the end of a season. Players can retain a role or other players get roles.
As for progression I saw an "A" potential Julius Peppers have multiple cold streaks during the year, his stats reflected it (only 3 sacks), and his overall took a nose dive of -6. Another D Line guy who was older than Peppers and with less potential got on a hot streak during the year, had decent stats, and went up a few points overall. I don't recall EVER seeing a "A" potential decline in overall...let alone a guy that's older and having less potential increase in OVR.