I've heard that putting snake poo where the possum sleeps can deter them from coming back as they think that a snake has moved in and don't want to hang around anymore....
the other thing they say to do is wait till the possum goes out for the night then fill up all the entry points into the house/roof.
I wouldn't risk letting my snake at it as the snake might get hurt and wild possums would have a lot of parasites which would be transferred to the snake, and how do you guaranty that your snake doesn't manage to escape or hide or disappear.
I don't think anyone would have tried it, and if they have, i doubt they would post about it..... it wouldn't be the kind of thing you want to admit too on a forum.