Currently, your BeagleBone is only serving your local network. You can enable port forwarding, like you did with your Tor server to open it up to the Internet to allow access to ZNC while you are on-the-go. If you do this, be sure that you are using SSL and consider using a Dynamic DNS service so you don't have to remember your IP address.

The ZNC and BitlBee packages are quite extensible. Moreover, since they are IRC servers, you can run an IRC bot in your ZNC server. There are several popular IRC bot packages and perhaps the most well known is Eggdrop (http://www.eggheads.org/). A custom bot on your BBB IRC server can interact with you from IRC to hardware. For example, if you add a temperature sensor on your BBB, you can query the bot to find out the temperature in the room. If you add a ZigBee radio to your BBB and attach the same temperature sensor to a corresponding ZigBee radio outside, powered by a battery, the bot can tell you the temperature outside. If you become an avid IRC user, you will enjoy combining the hardware electronics project with your BBB bot.

If you want to involve the CryptoCape to add some hardware protection, you could store ZNC's SSL certificate in the TPM. The TPM can store RSA keys and the keys can be generated such that the private key remains in the TPM. While there would be significant programming to connect the various components, this would certainly be a fun and challenging project!