There's an easier way to get that screen, just leave the Gameboy as is!
Steve - have you decided what the device is going to do? As in will it have a sole purpose (like a handheld Mame device) or is it more a tech demo of what you can do with the Raspberry Pi chap? Will it be full controllable using the standard D-pad and buttons or do you reckon you'll need to use a keyboard or mouse etc?
I'm hoping to have it controlled with the dpad and buttons with the USB ports free for a proper keyb and mouse or another joystick. It all depends on the software which is in the very early stages.
I have a feeling, just a feeling, that when this project reaches fruition...
It is going to rock, and not only that, but rock hard!
Good work Steve!
You have your own investor group here, awaiting results!