What would be nice is if part of the setup process asked you to choose the default OS app or an app from a third party. It would be mandatory that both the OS default and the third-party apps have average user reviews for the current major version number.
We are working on 4) Programmatic app submission and developer APIs and 5) Load a native app immediately by hitting a website/URL for Android.
We call it In App App Distribution. It enables any Android app to distribute other Android apps without Side Loading.
This technology can be used to create a browser that does exactly what Vibhu suggests. Some other ideas are an A/B Testing service, subscription service, house ads service, In App App Store or a bug fixing service. We are putting the beta together now. If you are interested please sign up: www.inAppSquared.com
Speaking as a user and not a developer (though I am a mobile app developer), this is a horrible idea.
I would be so pissed if I bought a new Android phone and gmail/Google Nav/maps/calendar/etc weren't preinstalled.