dual independently adjustable fans, or at least have the intake and exhaust at opposing sides to run the air across more surface area, as well as have it draw in cooler air, not the warmer exhausted air right back in.
heat destroys lithium batteries, so moving the battery behind the screen would definitely help in the long run, although dual batteries would also be nice
having multiple tiers would be great too, someone wants to pay extra for the core chip? give the option, not going to be able to stick user upgrade able sockets in systems this small, but at least it's the next best thing
my old Sony UMPC has the battery externally, which of course allowed them to release an extended capacity battery, the battery becomes a handle of sorts on the side of the system, so that's another option