If you're considering a similar pattern with Flutter rather than ReactNative, they call it "add to app" and there's a couple good talks on how others have approached this [1], [2] from the recent FlutterConUSA, as well as a couple articles that include details and case studies [3], [4]

I haven't tried this myself with a large project (just small examples as proof-of-concepts), but the approach seems very sound. One thing I liked is once you have the legacy app shell figured out, it's not a crazy approach to mock out the bridge/native services and run the app in just flutter (or react native) for development/testing acceleration, then adding final integration testing/QA with the full legacy app shell. I've seen some odd behaviors from apps that have used this approach that I would have to imagine can be serious headaches to debug. That said, it does seem the approach pays off long-term.

There's not much published online about it, but I believe Headspace has used this approach for its mobile app. See [5]

[1] https://www.droidcon.com/2024/10/17/flutter-add-to-app-the-g...

[2] https://www.droidcon.com/2024/10/17/successful-flutter-re-pl...

[3] https://docs.flutter.dev/add-to-app

[4] https://leancode.co/blog/flutter-add-to-app-overview-and-cha...

[5] https://www.nearcoast.com/headspaces-leap-to-flutter-a-game-...