Not sure if you have any modes or mini-games that would support this idea, but there's always been a type of mode I've thought would be cool since the introduction of color-changing LEDs. This would look coolest with something like CCR's playfield ramp LEDs, but could certainly work with the scoops (or any other lighted shots).
Anyway, I've always thought of it like a combination, where you need to get a pre-determined set of colors -- say left = blue, middle = red, right = green. All shots start as the same color, and each time you hit a shot, it cycles through a color set: red, green, blue, red, green, blue. The object would be to get all shots to match the combination. So, you need to hit each shot a certain number of times, and if you hit one too many, you'd have to cycle back through again. There could be a scalable difficulty by adding a 4th or 5th shot and/or a 4th or 5th color.
This would thematically fit with picking a lock, but could also be configuring / assembling something, mixing potions to a recipe, whatever.
Actually, a potential derivative of this would be recreating the old Mastermind board game where you need to guess a hidden combination of colors. In this case, you'd hit shots to select colors and then submit them as a guess at the combination. You'd then need to deductively figure out the combination based on your correct / incorrect guesses. Maybe something like this could weave into the riddles?
Anyway, not sure if this would fit with anything you're doing, but I thought it's a decent enough place to throw the idea out into the ether for potential future use by someone. I think it would be a fun mode.