I think that's totally fine. Different people have different ways of enjoying and exploring Tokyo. To me, the most sensible way of enjoying several days in Tokyo is to not really plan anything ahead of time (asides from knowing to avoid rush hour trains, Disneyland on weekends, outdoors on rainy days). Just have a list of interesting neighborhoods picked out as you say, then each morning let your whim take you to one or two of those each day. Then you walk around, browse around, see what great food you come across, just hang out. You may have high hopes for Asakusa only to feel like heading back to the hotel after a few hours. Then you may go hang out in Kichijoji another day and find that the entire day has passed before you knew it.