I know I should be working on more installments of the Megadungeon Training series, and even have ideas for at least two more installments. But I've been distracted by a discussion on Grognardia about ability scores (here and here.) There's a lot of interest comments on those posts, but I want to focus on the one of James Maliszewski's original points: the experience bonus for high prerequisites in OD&D. James wants to do away with these for his own games, because of "double dipping": if you use ability bonuses in addition to experience bonuses, some ability scores are going to provide extra benefit, while others (Con, Cha) won't.
But consider for a moment that problem here might be tying experience bonuses to specific classes. Since there are three (LBB) or four (LBB+Greyhawk) prime requisites versus six attributes, some attributes are going to do double duty for some classes. Further, a character with a high prime requisite gets that ability bonus no matter what the player actually does, which seems odd.
So, why not divorce the experience boost from specific classes? Any time a player solves a problem using methods that clearly rely on one of the six abilities, that player gets an experience bonus equal to ten times the character's ability score. Talk your way past a guard, get a 10xCha bonus. Bust down a door, get a 10xStr bonus. Pick the lock instead, get a 10xDex bonus. If the GM decides that's too high, don't multiply by 10. It's simple, provides rewards for non-combat actions, distinguishes characters, and encourages role-playing.