I see where your coming from, after looking at the cost of a standard li-ion charger, this project is not gong to be anywhere near cheap. this is starting to be a long term goal, mostly for use at car shows, meets, etc.
once built, charging would be a huge issue. idealy, I would like to use a ipod plug, mostly because ipod chargers and acc. easy to come by. but the reality is that it will probably use a cig. lighter adapter.
also, getting everything in a small, easy to handle package is going to involve alot of creative thinking/rearranging. even if I were to use the mimo screen, I still have to fit a battery, usb hub, possibly a charger, and assorted cables, without it becoming extremly heavy..