Okay so here's what I plan to do. Maybe it's not as appealing to you as to me, but I'm going to actually make the ring for arguewithatree. There are tons and tons of really, really fascinating minerals and stones you can make a ring out of that are far more beautiful than diamonds are already, and it carries way more meaning when you create it yourself obviously. I mean, yeah, it would take time and some tools that you may have to acquire that you didn't even know about before, but isn't that precisely what marriage is about?
My mother fell in love with a symbol on a truck mudflap in Peru. She drew it in her journal. My dad carved it out of wax and melted a bunch of old dimes down, then used clay for the investment. He made two - one for her, one for him. They're pretty cool. Me? I got my wife an Alexandrite from the russian Mafiya; she had a mokume game one made for me out of iron and gold. When people ask me where I got it I tell them I mugged a couple hobbits on their way to Mordor.
If you have the skills to pull it off, I think it's a fantastic idea. I've done a little bit of metal work in the past, but I don't have access to a kiln, centrifuge or a buffing wheel right now, so it would be a bit impractical. Also, I can bezel set a stone alright, but I've never tried to prong set a stone. I don't particularly care for bezels, so that idea is unappealing to me. Although I know they sell precast prong settings, so maybe it's not too difficult. Anyway, I wish you luck. It sounds like a really cool project.