Just to add my thoughts…
So you could make all your code remote, and push updates on the fly, what about if the user has no internet connection?
This is why we suggest people to keep all the code on the device. You could look into something like cordova-hot-code-push or ionic-deploy and bypass the app store approval process.
As for what can be an cannot be updated, it’s only the web code (html/css/js/img) that can be updated. With that, these cannot be drastic changes either. They need to be either small bug fixes, or content update. Any drastic changes to the app UI/UX needs to be resubmitted.
Also, any native code (cordova plugins) cannot be updated through these code deploy methods. They need to be recompiled and resubmitted to the app store.