I have some interesting evidence to suggest a very specific upgrade to the Thousand Sunny post Wano. I believe that Franky will put sea prism stone into the base of the Sunny!
Some of you might be saying probably not but why?
This brings us to my first piece of evidence in chapter 433 where Nami is listening to Luffy and Coby’s conversation post Enies Lobby.
So we learned that the Marines used sea prism stone to get through the Calm Belt safely(relatively) without going through Reverse Mountain. But why would the Straw Hats do this to their ship? Well a recent reveal in chapter 924 explained a bit of the origins of sea prism stone.
With this knowledge as well as what Kinemon states in the most recent chapter 951…
I believe that Franky will learn more about sea prism, particularly how to maybe shape it or possibly make it(less likely).
*Theory by Monstertrio333