I'd be a big fan of the Intel Iris chips for the next GPD. Give it quite a bit more graphics power, and wouldn't add a second chip. A low watt MX250 would be cool, that'd be my ultimate wish, but price would be very high and it'd be power hungry.
That said, it must have a keyboard. It isn't a UMPC without one- it's just a tablet.
The slider idea posted above is pretty cool- reminds me of this guy:
which I enjoyed owning. Those were a lot more expensive too- 2,500$ if I remember correctly.
Some gaming controls on the side instead would be awesome!