It sounds like a fun minigame, not as a primary gameplay mechanic. Remember that playing with a character isn't just a quick hour of fun, it can be a 10 hour packed experience. I think this will attract more japanese people but really in no way is this going to apeal in the west.
Personally I think Haruka should have not been playable at all if this is the only way to make her playable. Initially when I heard she was playable, I thought she would woop some asses as well. I thought it would be quite interesting to see Kazuma's adopted daughter to become a very strong woman eventually. I guess they decided otherwise and tbh i'm not happy about dancing as a main game mechanic in my yakuza.
I do have to say that those environments look gorgeous. I just recently got dead souls(finally) and from being used to that the yakuza 5 defenitly looks alot better.