Krantz's tip on changing the raws is accurate. I ran a dragon, and it's interesting to note some problems it has.
The most important thing to note is that you cannot eat. You can't pick anything up, you can't butcher for food, and you can't eat corpses. Even if you tear someone's arm off, you can't eat it. Because your natural attacks do a lot of laceration, you may be able to get by drinking all the blood that will be covering your body.
You also can't level your skills, it seems that the dragon's natural attacks don't count as biting and striking. This may be a result of dragons being nonsentient, and therefore not able to learn combat skills. You can still level your attributes.
Dragonfire won't work if you put the cursor in a solid obstacle like a tree or wall. Even with Temperature on, dragonfire does not burn wooden structures and doors.
Dragons can't fly.
Obviously most of these could be fixed by more raw modding.
It would be interesting to see if you could retire a dragon and then have a human adventurer recruit him. I haven't tested it, though. I'm going to go attack a castle and burn a city before I starve to death instead.
EDIT: NOOO!!! CURsssE YOU PATHETIC HUMANsss AND YOUR FIREPROOF DOORsss!!!
EDIT EDIT: Well, I slept outside the castle to see if anyone would open the door for me. Thanks to the city sleeping bug, I teleported into the courtyard (which also had doors.) Slept again, and then bogeymen spawned up on the walls or outside the walls or something, so I just quit. Did you know that the game has a different Quit message depending on what your cause of death would be?