Very interesting idea. Unfortunately, It's a bit difficult to present the idea in its purest form and also have it make sense. We can only speak about 10 thousand words, but we also have crippling arthritis, learning disabilities, and bubble life to contend with. Forget going insane, I'd kill myself out of fuckin' boredom under these conditions!

I actually think there are two very simple methods you can employ, one or the other, that could make such a world work without needing a million other things to have it make sense.

#1: people can download information directly into our brains. Kind of like the matrix. However, the Progenitors have controll over what kinds of information we are allowed to have. For whatever reason, they do not permit sign language or the like, and so it is not taught. Probably for religious reasons. something along the lines of "actions speak louder than words, but speaking with actions is forbidden." or something.

#2: People do not learn how to speak, ever. Instead, they teach songs, and these songs convey strong meanings in conjunction with body language. They are very ceremonial and used in special situations. These songs have been recorded, but using your life force gives the songs weight.

In both of these situations, people would learn pictures to convey simple messages. like a picture of a slab of meat might indicate that a building belonged to a butcher. It all depends on how much control you want the Progenitors to have over everyone's life.

EDIT: Oh yea, and interested! But a bit skeptical. Haha!