This blog is what I believe is going on with Punk Hazard as of the lastest chapter.
Law is there looking for something(obviously) maybe important medical research from the great Vegapunk. Since Law refer to Joker as one of Ceasar's toys maybe Joker is his version of a pacifista. He could've used a marine who is still active as the main body and only made one. The Straw Hats are gonna save or help Brownbeard leading him to feel the same way he did about Ceasar.(basically Luffy will be his new savior) And Law will find out what he is searching for and join Luffy in defeating Ceasar. Lastly Smoker will find out about Joker, havent guessed what he will do about it yet though.
Not sure who Monet's loyalty belongs to, she will be an interesting character.(we all have probably figured that by now)