All great points. I would just like to add that these things also work the other way-- with beautiful people being demonized simply for being beautiful. It's a fine balance to keep because convention tells us readers identify 'character' from certain physical/behavioral aspects in basic design, but by actively playing up to that criteria we feed into a closed system that never ends, while going against the grain out of principal can be damaging in other ways, like jarring the readers and making them question your motivations.
I think the bottom line is to carefully consider your tropes and be aware of where your inspiration comes from. Throwing in token characters (fat, disfigured, foreign, dark-skinned) is not a cure-all for an inherently slanted collection, but it's also worth remembering that in some cases there simply ISN'T much variation in body size, shape, and skin colour for a particular setting. Come to my sleepy town in Northern England and you will struggle to find anyone who isn't white, I guarantee it. We DO, however, have a man in drag with a long red wig and fake breasts who drives the local bus. You are free to make things as open or closed as you like, and that's okay. Keeping track of what you'er drinking up and spitting back out is always a wise thing to do, but it doesn't do much more good stressing yourself out trying to be a mascot for every possible type of person, either. You won't win that game, and at worst you might actually offend the people you're trying so hard to defend.
