Another possibility would be to have the offline wallet in a virtual machine without internet access.  Of course a virus could still get access to the file in which the virtual machine harddisk is placed, and thus the "offline" wallet, but the virus would more or less need to be tailored to attack your personal configuration.  So if you keep thousands of bitcoins, you definitely want a dedicated offline machine, but for anything less I would guess that the virtual machine - or even the setup you suggested above - would for all practical purposes be secure.