What is the sound of Beren One-Hand clapping?
sorry, couldn't resist...
Nevertheless, Bombadil as a Taoist or Zen Master makes a wonderful kind of sense (he could even be the Buddha). I wish I'd thought down that path before, so double thanks for showing it to me.
Naturally, we must ultimately accept Tolkein's word for the intentional vagueness about Bombadil and Goldberry ... but I've searched the Silmarillion for Valar or Maiar who might be them, and I have my own favorite unprovable speculation: Orome and Vana (see p. 29 of Silmarillion)