every quest line must have competing goals with all other quest lines, right?
That isn't how it works exactly.
"The Red Prince" has a quest to drink a bottle of Red Wine... Including Everyone Else if he clues them in.
Everyone else gets a quest to stop someone from stealing the bottle of Red Wine. Including "The Red Prince" automatically. This is regardless of your origin.
They can chose to do either one or to fight for it (or complete it first)
The way the game is set up... it isn't that every quest line has an entirely different goal depending on your origin.
That is why the origins are not exponential in terms of competitive questing.
It is why knowing the person's origin immediately gives away exactly what they are trying to do if they do not work with you immediately.
All this while ultimately everyone is on the same quest anyway (not four different main quests) so you have to work together at some point.
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Or rather this I am writing isn't how Competative Questing is done with Character Origins!
-Pregen Char 1: Has a quest to drink a bottle of wine
-Pregen char 2: has a quest to kill the winemaker
-Pregen Char 3: has a quest to deliver a bottle of wine to the cheesemaker
-Pregen char 4: has a quest to steal the reward money from the wine maker and cheesemaker.
How it works however can be!
There is a bottle of wine and you are offered a substantial reward if you can acquire it. You can
1) Steal it
2) Pay for it
3) Kill for it
4) Pregen Char: Wants to drink it
And you can chose any of these, fight for any of these, or attempt to solve it first or secretly.