I have to study this group for a while. Unlike Group A & Group B, it was easy to analyse and compare the characters' strengths and capabilities since they have a fair share of battle scenes. In this group, we have very little information on those new faces, except Chopper and Nami in whom we have seen fighting battle after battle.
Nami - Though she isn't physically strong, neither is she a DF user, but her weather manipulation skill is quite impressive. She can create thunder storm to strike her enemies and makes them electrocuted. She is also a "cat burglar" and an intelligent (and cunning) one even, who is able to look for openings to sneak up and attack her enemies.
Chopper - Whenever I see his bounty, I always laugh. The Marines think that he is the Crew's pet. If this is so, why do they put a figure on him?

Perhaps they feel that this "raccoon" (often mistaken as) could bite and the small amount of bounty on him would be enough.
Chopper, being a doctor, has been diligent in his research of inventing/creating drugs that could hype up his physical power. Hence his invention of rumble balls allowing him to transform into different forms in order to defeat his enemies. His most powerful form is "Monster Point" in which I think would be an advantage here.
Koala - She reminds me of Tom Cruise in Mission Impossible. One who works like a spy and sneaking into secret places. In Dressrosa, she has come to look for information and is able to get pass the Donquixote's family and steal it. I must say, she is quite a smart girl.
Kanjuro - "New kid on the block". He only comes about in Dressrosa. His drawings..... hmmm.... I can only

It is definitely in need of improvement. How he is going to make himself useful in this match, I wonder. Perhaps he can draw "stuff" that are harmful to the enemies, eg. a deep hole so deep that the enemies fall to their death or get injured?
Hack - Don't know much about him. But being a fishman, he should be pretty strong physically (like Jinbei for example). He is also an advanced user of Fishman Karate. If the battle is in the water, he will have far more advantage as he can breathe in water while humans can't.
I'm putting my votes on hold at the moment as I need a bit of time to think through before I decide.
