i know that linux depends on desktop environments to display things such as icons, mouse cursors, etc. but this time i'm using xfce and modifying a bit so that it looks bigger and has bigger icons and two huge panels!! this is made for elderly people and visually impaired people.
i think this has already been made by gnome and xfce has a lot of accessibility options, but i think there should be a desktop environment that is very user friendly, extremely user friendly, like gnome but way easier!! kind of like "sugar", the desktop environment used by the old "olpc xo-1" laptop, but for all ages.
In your efforts of developing a new desktop, I'd suggest to look around for already existing Linux desktops focused on visually impaired users. While they may go beyond what you're suggesting in your post (screen reader, text speech, braille output...) you may still get some inspiration from them.