Honestly, IRC <3 Combine it with a web application file sharing script or something and you got everything you need. Oh, and of course the entire VPN offline server concept.
If going IRC why not just use XDCC to share files... Again, set up a server, throw something like unrealircd on it and then use XDCC to transfer (example, check out the rizon network) keep it password protected, hidden, keep no logs, etc.
So here lets do this set up:
1. Server
Install nix distro of choice (I like debian) and set up your LAMP (Linux Apache MySQL and PHP) as well as an FTP server (proftpd is what I used) and then set up unrealircd for IRC server.
2. Gateway
This is your VPN setup to have the ability to connect to your server. I'm thinking maybe an adhoc connection between your server and the VPN and not allow the server to be accessible outside of the local network (will keep yourself, your friends, your files, even your IRC server off the internet and secure)
3. Router
Set up your router to have DNS run through OpenDNS, or an alternate DNS that your Gateway is connected to which is accessible via the internet (so you can tunnel to it outside of the network)
It may be a bit intricate, but a lot more secure then a lot of other setups out there
also for your server I would suggest set it up to use https only on an alternate port then the default. Makes it even harder to find. This should keep it pretty secure
