If the underlying hardware of the phone is compromised, then it doesn't matter what you run on top of it.

I am not saying that you shouldn't try rattlesnakeos just that the people you would be installing it for, still have access to everything on your phone.

If you value your privacy you would buy a simple dumb flip phone, solder out the microphones and cameras and use a wired headset. They can still get an approximate location of you through stingrays and such but it's better than nothing.