Besides the aforementioned Deep Dragon/Silver Dragon pairing, I'd probably split the Copper Dragon off from the rest of the Fan-wing clade.
Since (unlike the others) it has several spines projecting off its main wing-limb, whereas the Gold, Brass, Sand, and Incarnum dragons all lack these.
Interesting thought
Fiendish Codex 2 showed how the gods created life on many worlds- and on a lot of these, the life they created "opened the gates, letting the demons in to overrun the world"- very Stargate-esque.
Which is why Asmodeus wrote the Pact Primeval in the first place.
Maybe dwarves, elves, humans, halflings, orcs, goblins, etc, could all be the same species which each of the gods have customized to their own preferences?