AgreedYou can play anything in the world with a set of old style 14" (medium thin) hi hats an 18" (crash/ride on the thinner side) and (20" medium-thin ride).
Personally I've always preferred using a crash ride as my left hand cymbal which would make it primarily a crash. I find that I just prefer the sound of them versus a regular crash and it gives me a great secondary ride sound. I've played shows with just a crash ride and hats for my setup and it has always worked out perfectly well. They are versatile, and I tend to like the fact that my crashes end up with a little more definition while my ride patterns get a bit more wash. I use a 22 inch ride but you basically nailed my set up with that quote. Also using it as the only cymbal forces you to work on your cymbal technique and really learn how to vary your touch to achieve different sounds. Always a good thing I should think.