I want to run these theories by people to check if they're stupid. If they are, I apologize.
1. (less stupid) Could Hyouzo stay relevant post-fishman island? Oda set him up a LONG time ago, that suggests he is important. Of course, I realize that his importance could simply be him fighting Zoro on FI. Oda has also made it obvious that he has no emotional ties to Hodi and company.
I'm thinking he could stay around as a rival for Zoro. I'm aware you could argue that Zoro already has a significantly high amount of potential rivals (Definites: Mihawk, Strong Possibilities: Shiryuu, Mr. 1, Tashigi and Killer), but he seems to have a similar mind to Zoro (possibly a little more evil), just without anybody pushing him towards his dream like Luffy did.
2. (more stupid) Might Kong and Dadan be siblings. While not identical, Dadan and Kong have very similar features, mostly in their face.
A. Their eyes. They are pretty much the same, but Dadan has eyelashes. They're the same shape, they curve down the same way, they've got the bags under them.
B. The lips. They've got the same puffy lips.
C. The nose. They have similar hook noses with lines coming off towards their lips.
D. The ears. They both have tiny ears that poke out from behind the cheekbone.
E. Build. They appear to have a similar build. Kong's arms are admittedly far larger than Dadan's but they both have massive torsos and necks.
It would also explain why Garp would choose to leave Luffy and Ace with her. Everybody has chalked Garp's decision up to him just being a fool, but perhaps there was some sort of failed strategy behind it.
Let me know what you think. Find strengths, poke holes (call me retard)ed. I want more opinions on my theories. The second one is pretty wild, but I don't think it's so out there that it's impossible.