Fully agree. Android also has APIs to register another RCS client to the OS. What's missing are open APIs for apps to control Google's RCS-client. Indeed this

Fully agree. Android also has APIs to register another RCS client to the OS. What's missing are open APIs for apps to control Google's RCS-client. Indeed this would be convenient, but considering the potential for misuse there, Google would probably need a separate certification process for each app, which is quite a scale for something that didn't scale yet... A own RCS-client still requires accreditation to ensure interoperability with the RCS-service. API-access to Google's client would either require accreditation of the app using the client, or would need to be limited so dramatically that it's probably of no use...