I've argued for that same definition too. Note we don't even care if it's a moon (I'l bet the Apollo astronauts thought they were walking on a planet, and if life is ever found on Europa, we'll want it to be a planet too), or an orphan in deep space. A planet should be internally defined, like everything else in astronomy, and the definition should be inclusive (so that a "dwarf planet" would still be a planet!). Did anyone ever say "oh, we can't define a star that way, there'll be too many in our own galaxy!" It's kind of ludicrous. Now, a major planet, that's another story, and can be heliocentric.