The main advantage of cons pairs, in my mind, is that they're all the same size, so it's easier to reason about them and memory-manage them on a low level. They're also just as powerful as they need to be to support an expressive language. But that doesn't make them ideal abstractions for exploratory programming, especially when an equivalent abstraction in the same language takes fewer characters to type out and is even better supported thanks to 'map, 'any, etc.
I've been overly dramatic here too. I mostly wanted to help you make sure you were on a path that held water while giving you some hooks to convince me by... but I brought some external pet peeves into the mix and got worked up. XP Please do continue with your train of thought. ^^ Here's hoping the train mixes underwater hooks, or something.