I checked and the memento shop does have plushies, tee shirts, and books, though I never see the guests walking around with them the way they do the hats or balloons.
I'd still like to see a "large" version of gift shops or sit down restaurants that have actual displays and areas for customers to browse. I know some people have made workshop items to that effect, but the customers always clip through these things when you place them in a walkway. It would be cool if there were a way to actually have people browsing the wares in a gift shop.
I like the idea in post 29 of privately guided tour groups is cool. Another thing that real zoos often have are amphitheaters, where educators give periodic shows with animals trained to do what were once called "tricks" and are not more accurately termed "behaviors on cue," and of course with an emphasis on education and conservation. The San Diego zoo's bird talk show is really good, for example, and of course seal and elephant shows are always popular. I can only imagine the beautiful designs workshoppers could come up with if this were available. The trick, I suppose, is pathing, as currently guests can only walk on walkways, and I don't know if the engine supports creating non path structures where guests can enter.
I guess these aren't "shops" in the same sense, but they would definitely be cool.