I see you put a lot of effort into js-lingui and i must say looks promising.
A drawback i see in js-lingui is using template strings you can’t do things like nesting or formatted interpolation — not a big deal and i’m sure you will find solution for that.
Regarding translation of inline components that’s something react-i18next supports from start (and there is no need for a trans component).
As you wrap the messageformat module the resulting json files will be usable to be used in http://locize.com that’s a nice thing. Would be great your babel extractor plugin could submit directly to the locize service. If your module gets more traction we might add a sample using it to locize.com in future.