I think there are other, more effective, mitigations in place against the threats you are describing. First, there's no automated way to install CAs on Android. Users must do this step manually (the articles you linked are about Windows). Second, if you have installed a user-added CA, you get a prominent and permanent notification – non-dismissable, reappears after reboot – that your network traffic may be monitored. All this stops the "secretly-added CA" threat.

Finally, the current implementation is not effective at protecting against country-level MITM. Attempts at country-level MITM have been thwarted by browser updates to blacklist the respective CA certs, the same can be done on Android.

I agree those are legitimate threats that need to be addressed, but there are better ways to do so, which don't come with the convenient side effect of killing privacy research.