This could be done, but I expect it to be usually pretty annoying. Most of the time when I type I don't want to be looking at my hands or the keyboard. Instead, I want to be looking at either the text I'm typing or something else (like some other text, or a video, etc). Having a silhouette of my hands and a keyboard superimposed over what I'm looking at will just be distracting.

That said, I don't really have a better suggestion. Typing in VR is just going to be plain painful for anyone who can touch type with any speed on a physical keyboard.