If we could find a sutable laptop as a donner machine that had enough info available about it's screen inputs I reckon it wouldn't be silly to shoehorn an A9 circuit board in it.
Keep the hdd in normal location (or CF instead). Keep Li-Ion battery as they usually have the charging circuit built into the battery. I am sure the A9 circuit would fit easilly into the space where the motherboard was and just use some cable to connect up the USB and 10/100 ports on laptop case.
Ok it would need some thinking about to actually find a way to monitor the battery level as Li-ions don't like being run flat.