I agree somewhat that the Hunter could have a tree redesigned to become the "Ranger". I could see the same for the Rogue too. I fear it wouldn't be done right that way though and the playstyle couldn't be fleshed out as well if it was simply a "tweak" or attached to an existing class, simply because there is nothing like it in WoW at the moment. To truly implement a simultaneous melee/ranged physical character, there would have to be MANY changes, MANY new abilities, and all new talents. That's a new class.
Usually, overhauls of current classes to that extent never get done because it means removing a playstyle that other people know and enjoy already. When making an addition this big it has to be something entirely new. So tweaking current specs this wildly wouldn't really sit well with the playerbase.