So I'm working on a set of Star Trek Deep Space Nine write ups to follow up on my Next Generation post. Most of the characters are pretty straight forward except for Jadzia Dax and how to handle her Symbiont.
My current thinking is for a new trait (Joined Trill) that allows the character once per game session to add +2 to a skill roll. Claiming one of their former hosts had some relevant experience in this situation. That seems like a decent major trait to me.
I'm coming around to the simpler idea of just playing it as just as Experienced, probably at minimum of two levels. The only other thing that might necessary might be the Psychic Training trait. Sharing you mind with the voices of several other people would require some mental discipline.
The Trill show very little psychic potential in the series. I wouldn't add that. They do have ways to separate out the personalities of prior hosts and talk to them, but it's done so rarely I wouldn't make a whole trait out of it.
The Psychic Training trait just means the character has a stronger resistance to mental attacks. I was considering including it more on the idea that joined Trill are just stronger mentally thanks to the vast experiences.
No Trill shows any such mental strength in DS9 that I can recall. And since the Experienced trait gives the character two character points and two skill points, resistance to mental attacks will obtain if you raise your Resolve.