I've just seen this - if you're still interested:
I have designed many, and built some, RPi-powered laptops. They can be great. Historically, the LCDs have been the issue, but as soon as HDMIPi came out (which I have one of and is ideal for laptops), there has been a host of other displays, even the official one.
I often buy the rechargeable power banks for mobile phones to use for power - they give out a straight 5v (ideal for a Pi), often at up to 2.1A, last for a long time and have built in charging. One of the biggest issues for me is the hinges - I can never find stiff-enough ones, so that the display doesn't fall backwards a full 180 degrees - you can steal them out of a laptop, but they all have screw holes in silly places. I am working on a 3D-Printed stiff hinge for projects like this.
The enclosure is an issue - I've designed a Pibow-style acrylic layer one, which I didn't make because I'm not an acrylic millionaire. I still have the DXF files if anyone wants. If you have access to a CNC router, which I don't, then using that would help. I'm currently building a 5-inch laptop in a big altoids-style mint tin I got whilst on holiday - so using things that you have already could work well. Another cool option is to rip out the guts of an old, nasty laptop and put your bits in - that's worked well for me in the past. The circuitry isn't really hard - it can be solder-free if you want it to be, you just have to plug in all your USBs, etc.
Hope this helps,
Archie
