Some potential new roles I've been thinking about:
New Doppelganger roles
Advanced Doppelganger: An experimental advanced version of the doppelganger. Once per game the advanced doppelganger can Consume and Replace the target for that night. In game terms, the player who was the doppelganger is now out of the game (although he still wins with the dopps), and the player targeted by the advanced dopp becomes a doppelganger. This new form of doppelganger is unstable, however, and cannot have any other abilities. Any abilities possessed by the Consumed character are lost, including Mind Shield. The advanced doppelganger shows up as a normal doppelganger would to all investigative roles. Aliens cannot be Consumed, but the once-per-game limit on the ability is not used up if the Adv. Dopp tries to consume them.
Controlled Doppelganger: Unlike the normal doppelgangers, this one is actually responding to the Alien control waves. Since the rest of the batch is bad, they need to be destroyed. Therefore, this doppelganger works with an Exterminator Alien to help clean up the failed experiment and all evidence of it. He still has access to the Dopp chat, and acts in most ways as a normal doppelganger. However, the Controlled Doppelganger is actually on the same side as the Exterminator, and wins if he does. They are in contact with one another, and will have their own chat channel.
If examined by a Doppelganger Detective, their Controlled nature will be revealed. The Doppelgangers may use their night kill to remove a suspected Controlled Dopp if they wish. In case of a tie, the Controlled Dopp will lose.
New Human Roles
The Cult of the Great Old Ones are a group of Psychics attempting to summon their Dark Gods to this earth. To do so, they need human sacrifices. With the latest events, they figure doppelgangers and aliens should work just as well. Maybe even better. Each night they get a Night kill, just like the Dopps. They are an anti-town faction, and win when all other groups are dead. This includes Doppelgangers and Aliens. Unlike the other groups, they'll happily kill the Survivor Alien at the end of the game. They can use his blood, too. Although the Survivor will win in a tie if there are three groups left (he'll run away and the others fight it out).
Cult Leader: The Cult leader is an upstanding citizen of the town by day, and a cruel heartless fanatic by night. The cult leader will show up as 'No Role' to a Detective. Only a Telepath can determine his desire to 'Kill' each night.
Cultist: Cultists act like normal humans, except they are evil and have 'Kill' as a goal by default. Their Role is listed as 'Cultist', if they have no other profession. If they do have another profession, it must be a Psychic role, and a Detective will then both roles. I.e. a 'Telepath Cultist'. This should make up for the fact that the Agent will not be able to distinguish them from any other human.
I'm not thinking of adding these roles any time soon. We still have a lot of balancing to do with the current set-up. But I wanted to get them down somewhere before I forgot about them.