Next step would obv be to close a small exchange. Then, after several smaller ones, proceed with the bigger ones.
Then go after the miners. Then go after every retailer that accepts BTC.
It seems to me that the PBOC isn't going after Bitcoin. They're simply trying to prevent the outflow of capital from their country.
If you are serious about preventing it, you don't allow citizens to export 50k usd per year... especially in a country with >1bn citizens
Or you don't allow the buying of gold with unlimited quantities of CNY (which is like converting your local currency into an international asset and leaving the central bank of china to deal with gold imports and usd outflows)
I think the currency issue is exaggerated by sites like zerohedge. Meaning that even if CNY goes down, then chinese stuff become cheaper, exports increase (a lot) and there is a growing volume of USD inflows due to increased exports which then reinforces the balance of CNY/USD. There's a natural equilibrium in situations involving flows of capital, currency values and trade balances - and as long as you are a serious net exporter (China is), it's unlikely that many things can affect you.
The only argument I've seen about how China's reserves of 2-3 trillion usd are somehow "inadequate" is that they are only a small fraction of the local currency. Lol? Supposedly this is somehow "scary" if all Chinese wanted to convert their CNYs into USDs and the USDs run out.
Yet, this can only happen through some kind of international media campaign to undermine the CNY through FUD. And there is such an ongoing campaign both in mainstream and alternative western media. Even bitcoin-related news use false narratives (like "people are using BTC to bypass capital controls) regarding the CNY weaknesses etc etc, to artificially create runs to foreign currencies. Of course, if these gain traction, they become self-fulfilling prophecies. It's like bank runs. When people hear the X bank is unsafe, even if it isn't, they might move their money. And then when sufficient momentum accumulates by people moving their money, the bank actually becomes problematic and then the news stories are "vindicated" for reporting it early.