I think I see why this would be useful for things other than navigation - e.g. using avy to drive replacement or multi-selection, "select all X within this paragraph"-type things. But for navigation by word, for example, I tend to type only 1-2 characters to narrow down the selection, even for a character that is common on-screen. So I don't quite see how it would be faster to do what you're saying. I'm probably still missing something, but I don't know what.