I've tried this at open beta and it works, it should still work after launch which is 2 days from now. I will update this thread if it stops working.
1. 1st log in your US/EU bnet client, download the game client in your language, you can do this w/o purchasing the game
2. go www.battlenet.com.cn buy the overwatch game at 190RMB, which like half price compare to the global version.
3. open your us/eu client, at the log in screen where you can choose the region, choose "China' then log in and play
My battletag Barrax#5646
see you guys in game