High-speed rusting is a bit of a NetHack-ism, I admit. I'm fond of it because I like the notion of water being useful in combat against non-trivial enemies.
(Another idea: Wizzrobe + Water = What happened in The Wizard of Oz. This interaction should perhaps be kept a tad secret.)
My ideas for irritating the bosses are reliant on post-2.5 enemy technology, so we won't see that just yet.
Bubbles->Fairies is, as you know, a property of Magic Powder. I've simply redefined the transformation as a reaction that Bubbles have to powder of any sort. And the same applies to the gelatinous enemies. The Zol->Statue transformation isn't, I feel, too far divorced from the Buzz Blob->Cukeman transformation or the Black Chuchu + Light -> Statue transformation.
Awakening an owl statue is what Mystery Seeds did. Given that the statue can talk, its reaction to common sand is perhaps also a property of the statue. (Also, unlike the foolish modern owls, the ancient stone owls confer purposeful advice).
I can't help but laugh. Isn't that what Hyrule is?