Saying Facebook's plans are to become the "WeChat of the west" makes me even more wary. The first thing that I think of when I think of WeChat is "ubiquitous surveillance", especially governmental surveillance.
1. https://en.wikipedia.org/wiki/Rich_Communication_Services
However, as I said, this wouldn't be a dealbreaker. I wouldn't like using it as much, but it would still be better than nothing.
Also, it works without a data connection.
This is why FB chat, whatsapp, etc will never gain the traction that these services do -- putting time and effort into making them work is just a fool's errand until they open up the network to third party clients and make the specs an open standard.
When I hear people say "I'm not on FB", it mostly means "I"m on Instagram". People may know it's the same parent company, but they definitely aren't aware of how deep the integration goes.
Widespread norms can become just as powerful. Wait until insurance companies and employers universally require your Facebook account's medical risk and employability assessment ratings.