It's difficult to build layers on top of the Bitcoin blockchain. The base asset, Bitcoin, is volatile. Its volatility affects the assets on 2nd layers. There isn't a one-one peg between the 2nd layer and the base chain. You'd need to trust an oracle. In your gold example, you'd need to trust the miner for authenticity and their books. For use-cases with oracles, it's more efficient to use a database. There's no need to use a blockchain.
Some projects on Ethereum, like DAI, have explored these use-cases. I think they have not been successful. DAI requires high reserve ratio (1-1.5) to manage the volatility of the base chain. You're using 1.5 USD to get 1 USDDAI. It's not very efficient. I'm less excited about assets on blockchain. I think the market is not ready. We need to reduce volatility first.
Some projects on Ethereum, like DAI, have explored these use-cases. I think they have not been successful. DAI requires high reserve ratio (1-1.5) to manage the volatility of the base chain. You're using 1.5 USD to get 1 USDDAI. It's not very efficient. I'm less excited about assets on blockchain. I think the market is not ready. We need to reduce volatility first.