Ashley has alerady said what the solution is to the 50MB. however understand that I don't know how to implement this.
1. In your game. Make sure to check for updates. Some how you can specify a URL.
2. Export your game to XDK.
3. Remove game assets that are not part of the "First install screen". (ie UI, levels, audio).
4. Place the HTML export of your entire game at the URL
5. Pack the XDK GooglePlay version up to XDK compiler system.
no I'm kidding.
6. Players will download the game.
7. Upon first run the browse for update should go to the full games website.
8. Game should now download all assets.
however. i have not done this myself. But this is Ashley's suggestion for getting around the 50mb barrier.
I dont have the time to test this, but basically you export only a index.html that will redirect to your game's page, so the user effectivelly plays your website version inside crosswalks, and need a connection for the first launch.
Then since the offline.appcache (if you use it) will make it so ressources stays inside the app, and so you access your offline version whenever you want after this.
It is basically the same as the browser version logic, if I am right.