Whoah. OP is one of today's lucky 10.000 (ht XKCD). Let us introduce you to sign languages: natural languages evolved without a single sound. There are hundreds of these around the world, in daily use by many deaf communities and studied by academic researchers, many of them from these same communities or closely allied to them. Lovely convergence of ideas: these languages indeed involve ample use of the 3D affordances of the visual spatial modality. And they use these affordances in exactly the kind of flexible ways you would expect from a complex linguis...
Worth noting that the visual cortex already does project mental images externally using, for instance, the limbs. Human languages around the world make constant use of this, combining speech and other conventionalised modes of expression with depictions like manual gestures. The keyword here is iconicity, when the form of expressions does resemble their meaning (and this is why "our languages are symbolic" is only a very rough approximation of the truth; in actual fact, our languages are indexical, iconic and symbolic, and each of these offers its own cons... (read more)