Quote Originally Posted by Eldariel View Post
The major problem is, most creatures you could come up with can already be lumped to existing categories. Hell, it'd be easy to lump Aberrations with Outsiders and call it a day; most creatures you can come up with can easily fall into Outsider-type.
Well if you really wanna go with that "everything can be lumped into one of the categories", you can just scratch several of the types in 3E D&D. Why do you need "dragon" when "magical beast" is perfectly serviceable? As others said, "aberration" could go into "outsider", and Fey and Elemental too, as well. Humanoid, Monstrous Humanoid and Giant are kinda redundant when you look at it this way, as are Animal, Beast and Magical Beast (they already did away with Beast), and probably Vermin as well.

The question is - is that really desirable? The question may not be whether you can lump a given sort of creature with others, but whether you'd want to. As others said, "outsider" is way too broad, it might as well be split up. Not to mention that one's campaign may have new creatures that are different enough to merit a new type, even though you could shoehorn them into one of the existing ones.