That sounds like a pretty good idea. In addition to the effects-based rings that are already present in the games, I bet we could manage standalone spells through spell rings. There's precedent for that in other Zelda games; when the Great Fairies give Link the three spells in Ocarina of Time, they come infused in those [url=http://zeldawiki.org/File:Din%27s_Fire.png]crystal things[/url]. However, those are the most powerful spells; I bet the standard spells a mage calls upon regularly could be linked to gemstones small enough to fit on rings. Being a trained magic user is still important, though, because Link needed a magic bar to make use of them. Thus, in order to tap into the magic powers of a spell ring, you'd need to have like, awakened your magic energies through training or teaching or a gift from some mystical creature.

The passive effect rings can still be worn by your average joe and work because they don't need any input of magical power to apply their effects. The ability to craft a ring with a specific effect would probably be reserved to high level magic users, with all other rings crafted by chance through Gasha Nuts. Mid and low level mages probably buy the spell rings from jewelers, but they would be pretty rare and expensive so most people only have a few.

Does that sound like a good idea? Tying standalone spells to rare rings makes it very easy to understand what you can and can't do, but it also opens up opportunities for you to learn new spells as the story goes on without having to do like a long training montage of spellcrafting or whatever. It's also consistent with the source material, which is always a plus. Rings would contain weak and mid-power spells, but the big powerful spells would need to be channeled through items like the Fire Rod.