I don't think I've ever used them personally, but this is exactly the use case for "sticky keys" -- being able to press and release the modifier key (Ctrl, Alt, Shift) and have it remain "active" until another key is pressed. It's an available option on Win, Mac, and should be there in most Linux distros as well.

But that said, I definitely agree with the author that making your keyboard shortcuts customizable is a very useful accessibility feature. IMO it should be a standard feature. Should be standard for video games too, although there are still a great many games that do not let you remap buttons.