I wouldn't rule out Momo being Pluto so quickly.
I don't think it's so crazy that the issue of Pluto being a battleship is just a smoke bomb to throw off the government.
Also, Oden and Momo are from Wano, so there's no problem. Zunisha would not be Pluto, but rather those who control Zunisha. Just like Shirahoshi controls the Sea Kings.
I see 3 things that may be serious issues with this idea of Momo being Pluton , if there is a chance of it happening :
1. If Momo really is Pluton , Luffy has 2 Ancient Weapons on his side then , with Poseidon . Luffy having 2 super powerful weapons on his side is just a big no to me , especially now when we're about to enter the Final Saga next chapter .
Yes Shirahoshi isn't helping Luffy yet , but even Momo alone is already bad enough ( for me at least , if he really is Pluton ) . It will just kill the tension for me .
2. If Oda wants to make Pluton's residence in accordance with it's Greek Mythology like he did with Poseidon
Like i said in that post , Poseidon = Ruler of the Sea in Greek Mythology , and Oda's version of Poseidon resides in the Sea , i think this is done intentionally .
This could very well have been done to Pluton , if true then Pluton can't be Momo as he is not residing in the Underworld or anything like that .
3. What Vikas mentioned above - Momo being Pluton because he can control Zunisha will just make him a copy of Poseidon then , which is underwhelming/disappointing