[CuriousCosmic]

It's not that RCS doesn't work that way.

RCS support is actually embedded in android (albeit as a closed source rcsprovider implementation). They just won't actually open up the API (That they expose to other orgs that pay them enough like samsung for their apps).

There is no good technical reason why the RCS API needs to restrict itself to only pre-authorised applications vs making RCS access a permission for the user to approve.

[AAAAaccountAAAA]

If one is content with remote-controlling Google's proprietary implementation, it can unofficially be done by leveraging the Web UI: https://github.com/mautrix/gmessages

That however does come with all the drawbacks of adversarial interoperability.