The Traitor Player Character

[Duff]

Does your group intuitively understand when PVP is going to be included in a game or not based on the genre, campaign Pitch and everybodies character descriptions?
Have you played a few campaigns that did have PVP and afterward had games without?

If so, your group probably has established the bonds and has the social skills where you could get away with this.
But it should be a game where possible PVP is in The Pitch.
And I'd be inclined to make sure the traitor character does not get rewarded for their treachery until the epilogue

[Shpadoinkle]

I dunno, it seems like it would be a crazy twist that would be well-remembered

"Well-remembered" in the sense of your players going "This is why none of us will ever play with you as DM again," sure.

In the sense of FONDLY remembered? Yeah, no. Never in a million years. PCs screwing each other over isn't fun.