There obviously 'is' a way of doing it ... because the Gmelius Chrome extension does do some manipulation of the Nav bar! [For instance, it adds Google Voice to the bar; it replaces Google News with Google Reader, and Removes Google Play from the bar.]
Exactly how it's done I'm afraid I can't tell you - because I simply don't know! Perhaps they've found a way of writing some Javascript code to intercept the standard Google data ...?
Perhaps if you're a Chrome user, you could install that, and then make the suggestions to the authors (who from my own experience seem very responsive to comments/bugs, etc.!!). I'm sure they'd appreciate your idea even more after you make a small donation to them!!!!!!!