This sounds like another iteration of the EV certificate, whose value has long been debunked. The funny thing is that it's the browser vendors--including Google and Apple--that have greatly devalued EV certs for websites (i.e., you don't get the company name in the address bar any more, the green background, or any of the indicators you used to get). And now it seems that the very same companies have come up with another idea that's essentially EV certs for email.
I'd say the chance that Let's Encrypt will provide VMC certs is the same as the chance that they'll provide EV certs--none. And for the same reason: LE depends on the ability to issue certs automatically, and certs of this sort cannot be issued automatically.