I'm always willing to back up my concepts with content, but I know what you mean, all that thought behind a concept in order to keep the continuity of the game in-tact just to add a feature some people might not even really notice.
ADDENDUM: Let's do an example... For the very few of you here who have not played and beaten QFG1, don't read this...
Take Karl up on the battlements. He gives you information regarding Elsa von Spielburg, the Baron's daughter who has been kidnapped, and Yorick, the jester who has vowed to find and defend her. Asking about Yorick reveals many striking similarities between him and the warlock everyone keeps talking about.
Now, assuming that the character knows about Elsa, the warlock, and Yorick, the magic user
could use the Deduce skill and solve this little puzzle for Karl, which may gain you more skill points in intelligence, or perhaps gain you access to an area you would otherwise never get to, like the guards' barracks, within which you may even find a new spell scroll -- heck, a Meep had one after all.
Speaking of the Meeps, perhaps the Thief
could, in this hypothetical situation, Lie his way into the Meeps' coffers, saying the dryad had willed that they give up their accursed money or some such.
There's not that many situations I can think of from QFG1 but I'm not really talking about changing everything in the game; just a few bonus things for the character classes, which like the character classes themselves would add more replay value.