I like that also, a button to reset... It seems preseason stats are in there with regular season stats, I'd like to clear it after preseason, if nothing else.
As for familiarity... What you see in the scout screen is how familiar your players are with the play. When you get new players, they won't match up to the players in your team currently, which will reduce the overall familiarity. This system is good, in my opinion, because it gives two alternatives, better young players or older players more familiar with many plays. Finally, I think it really doesn't go up fast enough. If a team runs HB Strong Dive out of the I formation 20 times a game, I assume the coach will practice the defense against it over and over... familiarity doesn't take many seasons, in my opinion.
I would like to add that allowing player created plays in the game would spread out the familiarity and take even longer to really become familiar with plays.