The ipad is close to £600 in the UK. The ipod touch is less than £200. Given that there are tablet computers on sale for less than £200, and inspired by news of a future ipod touch add-on that gives it phone capabilities; how about designing a ten-inch screen, extra battery, and phone dongle that would take a (partially disassembled), ipod touch inside it and turn it into a ten inch ipad-alike?
One problem I see is that you would probably have to provide a service to take the users ipod touch and disassemble/assemble it inside the ten-inch "dock"; but Apple seems to provide a lot of monetary difference to try and make a profit.
Just a thought!