At 7", forget pocketability,especially with the specs you're wanting this would end being really thick. It would probably end up rivaling the HTC Shift or netbooks. Also, if you want to go this big while keeping both keyboard and gamepad, you're not going to want a centered keyboard. On a 7" device, a centered keyboard would need larger keys to be comfortable to use, which would clash with the space needed for the game controls. Also, even if you removed the gamepad to make this exactly like a netbook, thumb typing just wouldn't be very comfortable. Instead it would confuse people as whether they should be thumb typing or touch typing, just like HPCs and certain UMPCs of old.
Instead, for a device this massive with both kb and gpad, I would recommend a split keyboard. It would allow for the keys to stay small enough to allow room for the gpad to exist, yet easily accessible on both sides without having to need to shift your grip. It would take some getting used to, but if people can sorta get used to using the Wibrain or Q1UP's kb, this shouldn't be as big of a problem.