Pretty much this. She made the show what it was and S3 shows what happens when you loose your head.
If KyoAni are clever, they'll announce a S4 (that has Nagisa and Rei in actual roles this time) to come out on the 10th anniversary (that if they know what's good for them, will have very little ikuya). Then soft reboot it with a series on High Speed! Vol. 1 (something that's been missing since day 1 btw).