I think that is an excellent idea. Maybe take it a little further and have map "profiles" that allow you to setup a list of changes ("Programming" -> binds brackets, pipe, etc, "Texting" -> binds keys to common phrases ex. ctl-l => lol, ctl-c => I'll call back later, etc). I'm not sure if you can bind a single key to a character string.

Anyway, the main idea is that you could have a widget in the status bar that when you clicked it gave a dropdown of pre-configured "profiles" that could quickly easily change the functionality of the keyboard.

Back to the binding of a single key to a string, that I guess is almost like a macro recorder, and might be a separate idea/program, but one that I think could have a lot of power. For instance, thinking of being on the terminal. You could bind ctl-p to "cd /home/[user]/Pictures" or some other directory that you might frequently go and didn't want to have to type out each time.