Your take for a visually impaired friendly wallet is great. I would just like to add that, actually, Windows comes with a Text-To-Speech system (bundled with it Assistive feature) - officially known as Narrator. It is able to read webpages and read aloud the current selected widget. With that, I believe that web-based wallet (such as CoinSpace^) are already friendly enough for the visually impaired - considering that they have much more experience in using the Narrator feature already.

* I tested out the Narrator on CoinSpace and it is not that accurate. However, take into consideration that the visually impaired will most likely be used to it already (or that they are using some other proprietary software with more accurate result).