It doesn't seem out of place for Robin / Blake to take on the mantle. The Batman is suppose to be a symbol of hope. One that will inspire people. It makes sense for Blake to take this mantle and keep it going. If he goes his own path, then he has to start completely from scratch and get Gotham behind him. If he simply takes up the mantle, then Gotham has its Dark Knight, it's symbol of hope. Not to mention, it adds to the character. They already idolize him for saving the city. But imagine how they would feel if he reappears out of nowhere, again, when the city needs him? That's what Blake can do with the mantle. He can make The Batman reappear when the city needs hope the most. Driving the point home that The Batman is hope. .. With his own path / new outfit / new alter ego, he can't do that.
