Hey everyone. Been a long time reader of tvtropes, and just recently stumbled across this project. I really like reading all of these entries and I find making real world biological analogies to Pokémon is a very cool concept. However, I called dibs a bit too early after making a new account, so I didn't have the ability to notify the thread immediately. My apologies for that.
Anyway, concerning the Dragon-type, I couldn't find any preceding explanation for their unique properties in any of the Dragon Pokémon lines, so I'll have to come up with my own. My personal interpretation is that it has two parts, a sort of material that is found on all Dragons' hides that form the defensive component, as well as a specialized organ capable of generating a kind of energy as the offensive component. The material could explain Dragon's many resistances, due to the hide's highly unreactive properties to most elements except extreme cold and certain types of energy. The offensive component of the typing is a bit more abstract, so a mysterious form of energy that can be expelled from a Pokémon's orifices or infused into their attacks makes sense. The presence of the organ can also explain how some non-Dragon-types are able to use Dragon move, as they likely have a less developed organ for this.
For the type's history, I speculate that Dragons were more common in prehistoric times, but being weak to themselves caused most of them to go extinct or lose their Dragon-type through natural selection. The ones that remain are both rare and extremely proficient predators, and most of these pseudo-legendary Dragons have features similar to dinosaurs.
My main worry is that explaining the Dragon-type's advantages and weaknesses would also necessitate some interpretation of the Fairy-type's properties, like how they might wreak havoc to a Dragon's skin or absorb the Dragon energy. My interpretation would also introduce some new concepts like Draconium hides or Draconian energy, like another Regicite or Umbrate all at once. Would all of you be OK with a newcomer like me shaking things up like that?