One more thing drawing on my last post...
I mentioned the Chinese bird called the Peng. The interesting thing about the Peng is that its serpentine counterpart, the Kun, is not in opposition to it in any way. Instead, the Kun is a giant sea-serpent that turns into the Peng. This implies the same "necessary coexistance" as the feng huang/dragon pairing but takes it further, stepping from the external pairing of male and female into the explicitly internal alchemy of the transformation of self.
Kun is linked to the leviathan, and Peng to the garuda and the roc, but it's also notable that the character for Peng,鵬, is considered a variant character of鳳, feng, as in feng huang. The character鵬 is pronounced in Japanese ashō, and the Japanese name of the feng huang is hō-ō.
Incidentally, when he flies, the Peng is described as creating a whirlwind and roiling the waters. This is also attributed to the great eagle-jotun Hraesvelgr. Maybe not surprising considering they're both, you know, giant birds, but it's just an interesting little commonality.
And speaking of internal alchemy, there's also the Lightning Path/Serpent Path outlined for the Sephiroth. This is another way in which the Serpent becomes the Lightning. As a practitioner working with the firebird archetype, I believe both paths are complementary and there is value in walking both.