Realistically, it is hard to promote yuan as global currency because of the capital control. I'm not even sure if letting go of capital control is a good idea. Several experts that I followed suggested to not let go of the capital control because the risk is huge. But capital control also meant that other countries can't trust yuan fully. So why not use HK dollars. After all HK has done this role before, to become the gateway to China. Let it free floating, in the form of digital currency to make it efficient and low cost, backed by assets and multiple currency, especially yuan. If all Chinese foreign trades are settled with HK dollars, then it will be a powerful currency, enough to be one of the reserve currencies.