Customizable keyboard binding is a major and widely overlooked aspect of accessibility For example checkout this thread on mozilla forums about keybinding customization in firefox

https://connect.mozilla.org/t5/ideas/customizable-hotkeys/idi-p/4979

https://connect.mozilla.org/t5/discussions/hotkeys-yes-please/m-p/59929/

This along with modifiable context menus and the ability to share control schemes would greatly improve most software for multiple tasks.