I agree there is a real lack of flesh in the custom character. You don't feel like you are a part of the world like the Origin ones.
I won't play with an origin character ever, for me they are just good npcs. I loved playing with Viconia, Aerie, Minsc etc.. but i wouldn't have played any of them as main char. So sad Larian put so many ressources into Origin char instead of custom -a bad thing herited from DOS2 - but i hope they'll correct it for the full release.. Anyway

I LOVED Dragon Age Origin origin's stories and the impact each had on the game. That's the dream I guess. It's probably too late for them to implement this kind of prequel to the game.. Even just quick scenes maybe as flashbacks during sleep at the beginning ?
If not that, at least a conversation with a npc/tadpole would be a nice thing to add. But if it had no impact in dialogues options that would be sad.

But also, it would be great to meet people your custom character knew from their past. A good thing to add to the immersion feeling...