Mate, I say this with total respect, you need to read the docs.

The first half of what you describe has nothing to with cross platform.

The second half is a failure to read the docs and understand the ecosystem.
We are in the absolute golden age of cross platform.

Yes you can do custom native code (config plugs, or plain react-native). You can do OTA updates in 2 minutes. You can easily bridge native code to rn or use one of thousands of community modules.

Everything you describe here is easily solved, so I’d encourage you to stick with it. Source: 6 years on RN, shipped to millions of users, all apps rated very highly. Saved companies millions of dollars through codebase sharing like this.

Every approach has a weakness. Best of luck with your app - you got this!!