Interesting. I definitely want to experiment with something like that. Most examples I've seen of a WP theme in React (e.g. https://github.com/Automattic/Picard) use the new WP API and a node.js app. So there are (at least) two potential approaches to this.

Yeah, I considered that, and in some cases might take that approach.

But in my particular case the websites need to be server-side for SEO, so it's mostly just that I want to use React for reusability and because I prefer it over wordpress theming with php tags.

Furthermore, I can now use React and still deploy the site on a typical LAMP-stack cheap hosting!