All of the keys can be re-bound, except for the Escape key.  Since this key is the only way to regain the mouse/keyboard focus for the rest of the system, it would be nice if I could either re-bind it, or bind a new "secondary escape" action (i.e. leave Esc immutable, but allow another key to simultaneously serve the same function) to an easier-to-reach key.

Having to leave the home-row to toggle in-and-out of Minecraft is awkward.