My only point with 'late is to demonstrate a utility that needs a different implementation once keyword arguments are introduced to the language, and which may have no implementation at all if the keyword argument framework isn't comprehensive enough.
But yeah, I do think about redefinition a lot. ^^ Penknife's core library, when I get around to it, will be designed for people to be able to modify it, the way people do with arc.arc. I'm also trying to give it a module system that plays nicely with that kind of invasive coding style. It's for customizability's sake.