personal preferences aside Ben, it isn't very saleable without the restoration
an excellent example of that would be the Invasion of the Body Snatchers incomplete 6 sheet that sold on ebay a few weeks back, for just $149.
all that was missing was the bottom left panel, which is all text.
granted, a top 2/3 of a Rear Window is displayable and the IOTBS 6sh missing a panel is not, but if the owner wants to make money, the solutions are obvious.
personally, I would just wait to see if I can find the missing piece and complete the poster. It's a rarity to be able to do so, but there is always that possibility.