>This doesn't work in the cloud Software-as-a-Service model, because you are not running your own copy of the app.

Let me introduce you to scrapling+MCP--the closest I've come.

Stealthed, controllable browser gives you an API to arbitrary web things

You can't modify it, but you can extend it which imo is the next best thing

adb (Android) is close albeit a bit more tedious. It's fun watching an LLM take screenshots, read them, then send input events back to the phone.

If you have a rooted Android, you _can_ modify the apps. Xposed, ReVanced, et al subject to Play Integrity's ever growing pervasiveness