Comment by dozy

Patching an APK like this would break parts of the app, specifically the parts that are arguably the most crucial to be followed by pinned API calls. For example, in-app purchases via Google Play that validate the app's signing would all fail. Similarly restoring any previous in app purchases would also fail. Finally, you wouldn't be able to install this APK without uninstalling the valid production APK first, again due to signature/signing mismatch.