Show me 100 year old (or 200 year old!) reclaimed plywood and you'll have made me a convert.

I'm not so worried about earthquake performance because as long as you way, way over engineer you should be fine. The 3" teak isn't for strength (that's what steel is for) it's just so that it looks very solid.

For $500mm I would expect a safety factor in the high single digits. I know that's not what this house is about so I know it's not there, but I can't help but be an engineer.