Hey there!
Wanted to share that I created a couple of packages to make working with fluent and react easier. Both packages are in https://github.com/udacity/fluent-react-utils and are currently at their very beginning stages.
fluent-react-extract
This will parse your react source code and pull out l10n IDs and messages (and comments!) and compile everything it finds into an ftl file for you.
fluent-react-components
This one allows for custom Localized components to make reading and writing fluent-react source code more succinct. (It also pairs closely with fluent-react-extract)
I’d love to hear some feedback about these packages. As I said, they are still very much in their infancy, so anything that jumps out as a change we should consider, feel free to file an issue.