Web application in offline mode

I've been seriously thinking about a quick and dirty way to enable
give my clients the option of running my web application in offline
mode when they are out in the field with the possibility of no
internet connection. I am aware there are proper ways to do this (eg.
Google Gears) but I kinda want to come up with something quick - at
least as a temporary solution.

The rough idea is to package up the whole server, including Linux (yes
the entire LAMP!), and wrap it up inside a Virtualbox image. Then all
I need to do is the data synchronization part when they're online. I'm
yet to go into detail of the security part especially around the
protection of the application code and data but my gut instinct is
that it should work.

Any suggestions/criticisms appreciated.