So far this arc has been pretty good! I can't wait to see the rest of this falshback and hopefully see Sanji beat the crap out of his family! Basically I want to share my theory for how the rest of this arc will shape up and see what you guys think. I don't necessarily think it will be exactly like this but I think some of my ideas are possible. Its not super detailed its more of like a rough outline of some of the plot points.
First off the main antagonist. A lot of people are debating who will be the main bad guys this arc. Will it be Big Mom or the Vinsmokes? While it would be cool for Luffy to take down a yonko this arc he is nowhere near ready. Kaido has been hyped up constantly since the fishman island arc and every thing points to Luffy taking out Kaido with literally ALL the help he can get. The grand fleet, his entire crew, the heart pirates, the minks, marco, and the wano samurai. Literally as much as he can get. While on WCI he has the weaker half of his crew, a couple of minks (maybe even Pedro's old mink friends), Jinbei and the sun pirates, and maybe Bege depending on how that works out. I may have missed a few but you get the point. Since the yonko are in a stalemate then Big Mom and Kaido should be somewhere near the same level. If you compare the two groups obviously Luffy is not prepared to take on Big Mom. Not only that but so far this arc the people who most people hate is the Vinsmokes. Big Mom may be evil but all of her evil exploits are not really on center stage like the Vinsmokes' are. Another thing is that so far Big Mom has shown that you can make a deal with her of some sort (with Jinbei and Luffy during FI). With the vivre card and maybe with a favor or two she may be willing to let Jinbei and Sanji walk if Luffy helps her out.
This brings up what could Luffy do for her? Well Luffy doesn't really negotiate a lot but basically what I think will happen is either Luffy will have a little scuffle or clash with BM and then find he is not ready or he will be too drained after fighting Cracker to beat her. Considering that Luffy has yet to show up a half day after the Cracker fight begin I favor the latter. Nami will get her to listen using the vivre card and Luffy will say all I want is sanji and Jinbei. This is where Bege comes in. Bege is currently trying to overthrow Big Mom, however the crap he thinks that will work out. BM literally sees everything on her island so i doubt that she has not heard of it yet. Considering that Luffy is in front of her and she proabably doesn't want to deal with a weakling like Capone (compared to her) she will ask Luffy to take him out in exchange for Sanji/Jinbei's freedom. The reason that I think that Luffy will not fight the Vinsmokes for Sanji is just because I think that if Luffy went Gear fourth he could legit go one punch man on them. So while Luffy takes on bege Sanji, Chopper, Nami, and carrot will take on the Vinsmokes maybe Jinbei gets involved, tho I think that he is a bit too powerful for the vinsmokes.
This is perfect for showing the weaker members growth and help them to get stronger. Also unless Brook gets sidetracked from his quest with Pedro that leaves one Vinsmoke not taken out. You can probably tell that Reiju is who I have in mind. I think Oda is building her up to be reedemable and maybe even an ally in the future or at the least whatever the hell bellamy is. Maybe Nami or carrot will struggle and she will step in. Sanji may say something to her or around her that convinces her that her family is in the wrong or something along those lines.
Another part of this is that the tamatebako box will make the vinsmokes mad at BM after she gives part of the treasure to the vinsmokes as part of the gift exchange. This is will sever the agreement between them along with Luffy making the deal with Big Mom.
Anyway by the end Bege will be scurrying off WCI and the Vinsmokes will be controlled by Reiju. Reiju may join the grand fleet or she might just say that she intends to make Germa a better thing or whatever. Sanji will have finnaly become cool and strong again and Luffy will have helped Big Mom enough to get away freely.
As for actually allying with Big Mom I think that it is a possibiility that Luffy mentions that he is gonna beat Kaido to Big Mom or so that she overhears it. This may entice her even further to let him go as it will help take out the competition. Obviosly she probably doesn't think that he would be able to do much but it would either take out Kaido or he would get taken out which she would proabably not mind after FI. Maybe she even goes as far as letting Pekoms and Tamago go with the SH to help them out. I doubt she will go that far but its just a thought.
There are a couple of things that I don't really have an idea about like Jinbei, what exactly Pedro and Brook will encounter or how Chopper and Carrot will use the mirror world so I just left them out but Pedro and Brook will most likely succeed in their mission and Chopper will probably find Sanji and figure out how to help him or something.
Overall I think that this wraps stuff up somewhat nicely. Knowing Oda he has something that would make more sense and that will blow our minds but this is what I though up using some of the stuff mentioned. Hopefully you enjoyed reading it or you may enjoy picking it apart. Either way thanks for the read.