#13 should be even more generic: not just “Set default apps in iOS” but introducing something like the desktop OS X services, Android intents, etc. which would allow an app to start an operation with a type of data (i.e. a URL, an email address, a picture, etc.) and allow the user to send it to an arbitrary app.
You should be able to send a URL to Instapaper or send a picture in Dropbox/Facebook/etc. without making either one your default "browser", "photo viewer", etc.