And how exactly would that work?
Quest Giver: "We need you to steal this vital information from someone important to lead us to the location of someone we don't know.
Dragonborn: "No because I'm too paladiny for this kind of stuff."
Quest Giver: "You said no so we already have the necessary information."
You can see how many problems that would cause.
It's just a matter of perspective.
Quest Giver: "We need you to steal this vital information from someone important to lead us to the location of someone we don't know.
Dragonborn Option 1: Sure, I'll help. [quest goes as normal]
Dragonborn Option 2: I'm not a thief/assassin/paladin/whatever, perhaps you should ask somebody else. [x amount of time passes as a way to pretend the finding and completing the quest by another character, before the next quest pops up. You do not get the rewards you would usually get if you had done the quest, only the flags are set to keep the plot moving forward as it were.]
Dragonborn Option 3: I refuse to do this and find even the idea of such an act reprehensible. [essential tags are removed, now possible to kill the quest giver with all repercussions of having done so. Or just walk away and now it being impossible to do the quest. Cleared from journal.]
Dragonborn Option 4: I've no time for this. [quest giver stops talking, maybe going so far as then removing quest from journal, but still possible to return to quest giver to complete]
Unless the coding portion is crazy-difficult, the biggest problem would it just being time consuming.
Naturally all these options could be better fleshed out with more detailed alternate paths and so on, but for those that just would like to say 'no' it'll do the job.
PLEASE do. I will instantly download and endorse. In fact, I'll even help you beta it.
I just may take you up on that offer.