I would settle for a single good story that was only available to custom characters.
The variables you are offering are shared with the origins. But to answer your question, I would create a decision tree like this:
*if chacter origin --> don't add new story
*if race = gith --> gith background
*if race = drow --> drow
*if race = tieflin --> tieflin
*if class = arcane spellcaster --> arcane
*if class = divine spellcaster --> divine
*if background = noble --> noble
*else --> commoner
Or just create 3-6 stories and let people choose another tag so custom character can have as many tags and quest as orignins. That would make it even and fair. But I suspect that having less content for custom characters is the way they have to pressure players into chosing one of their NPCs. And that was one of the reasons I never quite got engaged with the divinity story. Custom characters were like sidequicks to their origins characters and origin characters didn't feel mine. So I hope that doesn't happen. It would be disappointing.
Last edited by EMC_V; 11/11/20 06:52 PM.