My feeling about origin quests for custom characters is that it would be far too easy for them to guess wrong. For instance, my current character is a ranger who grew up working in her parents' leatherworking shop. (aka guild artisan background). It's hard for me to imagine that a generic Guild Artisan quest would fit seemlessly into her story. It seems much more likely to me that the inclusion of such a quest would feel like Larian telling me who my character is. If I wanted that, I'd play an origin character.
A valid point. One excellent way to introduce a Personal Quest for custom PCs would be to have it revolve around something that happens after the game begins. (Think Dragon Age: Inquisition. The character gets the mark at the beginning)
I do think finding a way to add a custom PC quest line would be excellent. Maybe even introduce 2 or 3 different ones and let the PC decide which one fits their character best and follow that path. Currently custom PCs have no voice, no history, and come off as props.
