A long time ago, the Tower of the Americas in San Antonio had a small 4D show called "Skies Over Texas". I don't know if it's still there as I saw that a decade ago, but the seats were EXACTLY the same as Shrek 4D. There was one effect in that show that made it stand out above other 4D theaters. The entire theater/motions seats were on a floor that swayed left to right; pretty significantly at that. It would sway ten feet in each direction.
As the theater rocked, you didn't notice the theater moving, but you felt it. It really sold the idea that you were flying in the skies following a helicopter. It was a cool twist to your typical 4D theater and have always wanted to see that implemented in other 4D shows or other simulators.
This would be the perfect opportunity to do that, but there's no space or placement to put the system behind the walls to make the theater do that. I know this will not happen, but I'm disappointed to see that not done anywhere else. If you're in San Antonio and that show is still there at the Tower of the Americas, I recommend you check it out to see what I'm talking about. Hopefully it hasn't aged terribly.