Ben,
I've been enjoying your builds for a while now and liked your Portable 3D Printer build. Especially your upgrade to the 3D Printing Briefcase. In those episodes, you illustrated the fact that you don't have to be confined to the designs already available. And it shows that we always want to improve upon our designs.
The next logical upgrade to this system would be battery powered so you can truly make it portable. However, I'd like to see an integrated computer/tablet into your Briefcase. Since you can't slice in the control panel, and the software already exists for this, it IS possible. But being compacted into it would be a challenge. (And Totally Freaking Awesome!)
A tablet will give you a touchscreen, a 9 inch laptop will give you a keyboard and touchpad, or possibly a monitor on a Raspberry Pi would just be awesome. I'm not interested in the wireless Bluetooth option to work it by phone, because we all know how easy it is to loose your phone and all the data saved on it. And I wouldn't leave my phone while it printed either.
If that's too challenging, then the battery idea... Or both.
Thanks for reading.
Edit 2-9-14: I rescind my challenge. It seems 3D printers has been overdone on TBHS. And after partnering with Printrbot, it seems a final "briefcase printer" has been made and the battery part looks like it was already addressed.