Maybe someone needs to develop/build/sell a "Shield Mother Board" Where there are multiple female shield connector positions layed out side by side (or vertical, or both say 2x2, 4x4) , with one position having male pin shield connectors to plug a arduino board upside down. It could be a total passive board, or just add a power connector, reset pin, and a transistor isolated LED for pin13 (because the arduino would be mounted upside down). Maybe one of the mother board edges could have screw connectors of the shield pins avalible for off board wiring interfacing.
May not be a big seller, but would give project builders another form factor to work with. Might have to include mega shield layout for maximum compatiblity? Or two versions, mega and non-mega.
I release this idea to the public domain.
EDIT: just saw the "DoubleWide ExtenderShield" and "DoubleTall ExtenderShield" posted while I was typing this, same concept just more positions and a position for the arduino.