Had a speculation
Franky's previous bounty was of General Franky
Franky's new bounty poster is the Sunny
What if this is foreshadowing that Franky will do updates to the Sunny in order to turn it into a mech?
If we were to play around with that idea, perhaps it might be worth it to consider the possibility that the Sunny could be destroyed and then subsequently rebuilt with upgrades.
In Egghead, both of Luffy's rivals had their ships destroyed. From this pattern, Luffy is next.
At the moment the SHs are facing an unprecedented threat, Saturn of the Gorosei, along with an admiral, CP0, 9 VAs, and inevitably the seraphim. Them losing to Saturn wouldn't be out of the question. Especially since the goal of this arc isn't to defeat Saturn, but rather to escape to Elbaf.
With Luffy having massive win after wins in the new world, beating Doffy, then the BM commanders, then Kaido it would be more unexpected for Luffy to lose than for him to win.
When you look at Yonko flagships, the Sunny doesn't seem that impressive.
The Queen Mama Chanter absolutely dwarfed the Sunny. Were it not for Wadatsumi, it would have destroyed the Sunny. As a yonko, Luffy needs a top tier ship and I believe that the destruction of the Sunny would provide an opportunity for growth in this regard.
But what about Franky's dream? Well that's the thing. I think that the destruction of the Sunny could provide for immense growth for Franky.
In water 7 we were told that were a Ship's keel to be damage, the ship is basically waiting to die.
However with all the knowledge Franky gained over the timeskip, I think there is a real possibility that Franky could save the Sunny even after it has suffered catastrophic damage.
This ultimately leads back to the idea of the Sunny becoming Franky's new mecha. With the updates he makes to the Sunny post-destruction, it will allow it to turn into a mecha stronger than general Franky.