I mean, I agree this is Elon's dream. But so is SpaceX and Tesla which he did quite well on.
Also - you're quote reminds of the oft cited henry ford quote:
“If I had asked people what they wanted, they would have said faster horses.”
Google didn't start adding the ability to do flights in the search engine because nobody was using that. People love one stop shopping.
Honestly I can't follow the example at all. What does banking (one thing billionaire genius Musk wants to do on twitter) have to do with sending 140 character text posts? I don't see any kind of connection there at all.
Meanwhile Flight Search is a type of Search. The name kind of gives it away.
It better to think of WeChat like an iPhone as opposed to Twitter. So rather than opening up the Amazon App you can navigate to JD's store on WeChat. Obviously if you don't use WeChat / Twitter then them gaining a app store-lite feature isn't useful to you but cross-selling is a successful practice.
I'm sure JCPenny / etc would love if you could buy on Twitter though. Replace ad fees with just a simple %-age cut of the sale.
And no need to spend 44,000,000,000$ on twitter if all you want is to destroy the brand and replace it with a letter brand that's ungoogleable. But hey... what do I know.