As a player, how would you feel about a scenario where the likelihood of survival or winning is extremely low?
I'm in the middle of writing a one-shot scenario where the odds of surviving are severely stacked against the players. In fact, in my mind, its a much more enjoyable (for the player) ending if they don't survive. I've even run a few scenarios in the past where they were written so the players could not survive and everyone seemed to enjoy it, so I don't think it will be a problem (as long as its a fun game).
My purpose for writing this is for a convention, where the characters will not be re-used. However, I wanted to get other Keepers' experiences and thoughts on this subject.