I think it's important to understand that your elements are just how you see the world. So if your Cloud Evocations include some of water and some of air and lightning and whatever else, that's fine. Or if your understanding of water includes order and cleansing instead of entropy. Every practitioner doesn't see every element the same way and won't use it the same way. So (in my view) many of them could be narrower or more broad in range depending on the array of effects the player could explain (and the practitioner could wrap his head around) using thatelement.
And I agree Tedronai, many of the elements I listed (off the top of my head during a lecture /shame) step on other elements' toes. And a practitioner who understood the elements through a gazillion element system and chose 3 closely related elements would likely have a narrower range than someone who chose very different elements. This would be an issue with such a system, but not much of a handicap (just fewer maneuver options) in play.
Still, I can see the attraction of choosing something like Water, Ice and Blood. You want to be a kickin' water-witch (or waterbender, lol)
In fact, I think it would probably be a good answer to my original question of how to make a specialist keep up with someone who has full-blown Evocation. (With 3 related elements, you can take multiple specializations without running into the column issue).
And yes, obviously this bit of business would not be for every player or every practitioner. If it's a mechanical limitation, I'd think it relatively mild, but crazy element systems could open up options for players who were into that sort of thing.