Restless Spirits don't have conventional active roles either. They can't do anything during the night or day, unless they're killed. Then they get a vote just like anyone else. They don't have killing power, they can't give new insight to the game other than what is offered in the thread. My guess is that they were added for the sake of balance.
No host is perfect. Evil changed the Mafia Detective role for the first time when I was Mafia the time before last. He didn't tell anyone beforehand either. We were thrown for a loop, but the change wasn't something I disagreed with either. I'm not really trying to compare hosts, all three are different people and I'm grateful for them giving up time out of their day to host. So don't get me wrong. I just don't believe turning the game on it's head or removing some of the conventionality everyone is supposedly used to is a bad thing. It offers something different, and it looks to be a trend since the Mentor role was introduced two games ago. New roles were talked about prior to the game, so it's no surprise that some were added. There aren't set rules, like you have to have a certain number of Regular Townies, or even have one at all...past games prove that. Some games have even lacked a Sane Detective or Sane Doctor.
That's all I'm going to say for now, so I'll shut up. But I just can't agree with the sentiment that the role distribution is set in stone or that it has to follow a certain blueprint. It's still Mafia, it just adds a new wrinkle to it and it doesn't bother me really. It might have been a bit too much all at once, I couldn't disagree with that.