Subway Specification Stickers

This is so simple an idea I'm sure there's some bloody obvious reason it wouldn't work.

You know those fast-food-type restaurants where they make a sandwich or a burrito or the like by keeping all the ingredients along the counter behind a glass sneezeguard, and you walk along it, explaining to the person behind the counter which ingredients you want? And how if the place is busy, you have to repeat yourself three times, or attempt to communicate your desires by mime?

They should have transparent stickers with the names of all the ingredients, laid out just like the tubs of ingredients, on the sneezeguard. Then you don't have to speak at all. You can just touch the names of the stuff you want on your sandwich. Since it's glass, the food maker can see you; since it's direct and two-dimensional, they don't have to try to work out lines-of-sight on the ingredients as you desperately point. (They do have to be able to read backwards, but that's easy enough with a little practice.)