They have been doing that already. But Hong Kong's strength is its financial markets. They need to pump up the stock markets, by creating more value for investors rather than restricting innovative Chinese companies.
The stock market, as its current iteration, is more a gambling den then proper reflection of the actual, physical economy.
HK's role in the greater scheme of things to China is as latter's buffer zone, as whoever and whatever try to f--- with China's economy will have to contend with conducting their "war" on "battleground HK".
It's said that George Soros got his tentacles burned more times than he wants to count.