We know police are on the PPD, Acker and Sean are two. I am sure there are more. Would it have played better if the Wu character was a wesen. You could have had the character providing evidence that only a wesen would know. It would have been interesting that as Nick became more of a Grimm the wesen officers information would start to make more sense.
Looking at the cast photo Wu being a femal police officer would balance the group. Plus would make for some interesting crime scenes. Just like Trubel would add information because she saw a suspect woge. The wesen officer would do the same thing, except would provide the information without the wesen part. When Nick would ask how do you know she would just say 'Trust Me'
But if Wu was wesen what would you do with Hank? He would truly be the odd man out. We could go really sci fi and make Hanks secret that he is a genetically modified soilder.
With the way the show is going this would not be a far fetch from what you have. When the show started you had policeman solving crimes. When the audience obeserved wesen activity we where suprised and shocked. Now wesen activity is the norm. We expect everyone to be wesen. The fact that joke about maybe this time it won't be wesen. Sense this is the world the show has created then make the members fit in. Now it feels like a wesen world people visit. Instead of people living among wesen. That is one reason why Juliette beoming a part of this world fits. Comments keep wanting Juliette to be normal, the world she is in is not normal. Monroe seems more of a partner to Nick then Hank does. With each episode Hank gets pushed more to being a side kick then a partner. Other then proving muscle what does he bring to the table.