II kind of wish there were additional non-companion origins to explore
Same. Certainly the origin characters achieve that, but unfortunately that's not the same at all.
Still, I see so many interesting possibilities with dark urge. How about a Selûnite cleric who wakes up one morning with this new rot in them. Or a paladin? I think the internal conflict will be delightful to see how it develops.
Even with a more neutral character, they still likely don't want to bathe the Sword Coast in blood, so they'll have to resist this in a way that's likely more difficult than for the goody goodies.