Matthew

I think he is a spy but not for the government. I think he is for Garp. After the events of God Valley in the Manga, I think Garp is in the Marines but closer related to the revolutionaries than we know. I think Kuzan helping to catch Garp has to do with this plan. Garp stayed with the Marines to help protect the small guys and keep them from getting to corrupt but he is definitely going to side against the world government when the war starts are he know the celestial dragons and elders are evil

Unless the theory is Ryuma was sent to the future, then this would create continuity issues as Ryuma died about 400 years before Thriller Bark. But why would Toki have sent him only 400 years in the future instead of the roughly 800 years she jumped or even further to the time Joyboy would return

This theory has way too many holes at this point. Oda could make it work if he wants to but the holes make believing it impossible imo

I suspected he would have this Haki as soon as he was shown meeting Luffy.

Luffy is going to have to learn the haki Joyboy left in Emet to defeat the elders and Imu and he needed someone to teach him. Now he has someone that can t2ach it to him or at least he can observe to figure it out like he did with his observation/ future sight

I'm not getting into spoilers but the Manga clearly answers this question and who Luffy's up coming opponent(s) on Egghead.

It is about to get a lot crazier than this article suggests.

This new system isn't more powerful than haki can be. Just look at what Joy Boy stored in Emet and what it did to the Elders and even affected Imu who was far away. The strongest haki can overpower whatever they have

Vivid is definitely a D. That's been explicitly stated. We don't know exactly what it means to be a D. Blackboard and Law are also Ds as was Ace. It is more likely that the D traces back to a group from the void century whether a pirate group or a group like the revolutionaries or even something else. It is just known they opposed the celestial dragons

With how the Manga talked about the end of mission yozakura family and hinted at a new mission for them after defeating Asa, I wouldn't be surprised by a sequel mangʻa following the twins. Although it just might mean they aren't done even if the Manga is soon

First Enel should be much higher on this list. Second Yamoto should be here. Both should be top 5 on here. I also wouldn't include the Serphim who are both synthetic beings and don't even have man made devil fruits.