The idea of the "City life" is basically what characters will be told they had done with their lives up to the point of the Disaster. It's the alternate history that they won't remember when they "wake up" (enter the game), but the NPCs will expect them to follow. Generally speaking, City-related things should still fall within the realm of possibility for your own character but should not be a wholesale rewrite of canon.

We already have one character who can see ghosts and spirits in the game, so having another with a type of mediumship like that would definitely be something we could get behind.

It kind of seems like you're misunderstanding how memories are played with in the game. Upon waking up in the Cave (entering the game), characters only remember their canonical lives and cannot drum up any memories related to what all of the NPCs insist is true. Memory rehabilitation occurs either when a character breaks a law, or the player would like to haul them in for a routine rehab — it's sort of in the place of "curses" or the like in other RP games. These memories only temporarily overwrite any canonical memories before turning into a second set. Does that make sense?

As far as being a lone canon warrior, I wouldn't worry too much. We have very few canons with more than one character in the game, and they seem to be doing fine with reaching out and receiving CR in return.