Oh, you're right. My bad about that.
However, I don't really agree with the distinction you're making here....
It's not like Ace/Sabo are his decades older brothers, they're ultimately just random kids Luffy met at a young age, and that were stronger than him. There was no reason for Oda to keep them above him, especially wrt Sabo on Dressrosa, since Luffy was already experienced by then, and Sabo wasn't needed to protect Luffy from Doflamingo. We do know that Oda is willing to have the younger sibling be stronger (Katakuri/Pero) so this was just a rare example of Oda being willing to make one of Luffys ally stronger then him just because he has plans for that character, and wants to hype them as super strong
(Worth noting that Luffy has surpassed Sabo at this point, and could surpass Loki too,just in an arc or two. It's a bit hard to tell with Luffys power progression being all over the place)
Depends,this arc has been a bit vague on what the sun god Nika even is. The other giants acknowledge that Luffy has the Nika form, but they still all dream of being like Nika themselves, and they all have different interpretations on what he could be. And while he probably will have to acknowledge that Luffy is the sun god who will change the world in a way he can't, it doesn't mean that Loki's role against Imu isn't also being established. He ate the mythical zoan that Rocks dreamed of Harald eating, and with Oda mentioning 3 other gods, it isn't really out of the discussion that Loki could just be a different god, who's equal to the sun god.
fair enough, my point was more so about age. Hancock could conceivably be considered a new gen character