The 4 Gods are the most important figures in the Harley text though, so it wouldn’t make sense for some of them to not be featured on the mural.
If Loki is co-Sun God, then he is effectively the co-MC of the story, which would just be a dumb writing decision imo. Also, why is it never mentioned in the Harley text that there are 2 Sun Gods?
The 3rd world is not depicted on the mural either and its Giant childrens drawings. Its meant to be abstract. The Harley text a totally different source of information. We dont know what is on the drawings vs the text.
It does not make Loki, a character who appeared after 1100 chapters, the Co-MC just because he shares a title with Luffy.
Anyway, Im just telling you whats already been stated in the manga.
- Loki calls himself the Sun God and a Destroyer in his introduction.
- Elbaph citizens argue whether or not the Sun God (which is never stated as Nika) is a Liberator or a Destroyer
- Rocks implies 2 fruits are needed to topple the WG and one of them is Loki's (so your MC point is moot anyway because Loki necessary to Oda's endgame plot regardless of his title).
- Finally this chapter just straight up seems to imply both of them are the Sun God from the Harley text.
You can also literally deduce that Luffy and Loki are the one that havent met again until now, since they were allegedly split. Imu does not recognize Loki's power, which basically insinuates that when Joyboy was Nika, nobody was the Dragon in that era. Shanks is basically the reason both are meeting right now.