Hi,
I have reviewed your requirement and the same kind of requirement I got from one of the media house 1 year back.
The biggest problem in the offline browsing is at last for one time user need to download your website completely to see all pages offline. If you will think about user perspective it is a huge data consumption.
I will recommend you to make Android and iPhone app, to simply push the content on the user device. It will be sustainable option and event will not cost more than between 40-80 Thousand Rupees. I can make android and iPhone app where user can put your site data download in background mode or for new content he will get a notification.
Please let us know if we can further discuss over the chat.