Fine emeralds do not come by truckload - as long as the cut s not overly shalow and windowed, the shape is entirely your choice. I am not sure I understand what the issue is: are you considering a cushion cut emerald versus a step cut? The sahep is not very common, but then... nothing is very common about fine emerald.
Oops, don't know what happened to above post. I've never seen a cushion cut emerald but found a pic for you. It's a Georgian piece. Can't get it to post so you'll have to look here http://www.liveauctioneers.com/auctions/ebay/115454.html
Excellent Maya. Don't give up on emerald because of the treatment issues. It's not as much of an issue with the finer stones, and an expert independent appraiser can keep you from making a wrong choice.
Emeralds are the "queen of gems", prized since the time of Cleopatra. They are not likely to disappear quietly into the night.