Your keyboards could become THE choice for visually impared people. If the letters were much larger and in a simpler/crisper font they would be a big help to people who struggle even with the existing large-font keyboards on the market. We bought one of yours for my Mom and the letters just look like bright blurs, and not as large as her existing KB. Tall & wide but not "bold", in a simple font would be perfect. Don't underestimate the potential market!! Mock up a few caps and we'll test them for you.
