And if they have a whole route for an origin character who is an antagonist to the others that would certainly be something. Not exactly interesting to me, but it would certainly make the "Evil Route" make more sense.
Working against the other players in multiplayer?
I wasn't think multiplayer, but a scenario where say, you're put nearer the goblins, and the other origin characters, who are just NPCs now, go through a version of the Grove quest, so you're at odds with them, probably killing them in the process, like you do Wyll if you never recruit him before attacking the grove.
When I said Parodying murderhobos I was talking about that phenomona in D&D not specifically the people in the EA who have been playing through the first act so many times they've turned the game into Westworld.