Assuming that I have a server with Ubuntu server newly installed on it. I was thinking of installing the very same version on Virtual Box (Or any other virtualization software), connect it to the internet and use apt-get to only download the packages for upgrading the system and the new software such as (tomcat7, openjdk6-default-headless..etc). Then copy the downloaded packages from the archive folder to the offline server's archive folder through a USB stick.

So now the virtual system won't actually be upgraded nor have any new software installed. But would running the very same apt-get commands on the offline system without the download directive -d be executed without issues ?

*EDIT:*This needs to be as simple as possible because I'll have to write a guide for our client to do this on his own and so it won't be acceptable to require deep Linux knowledge to do this.