Honestly, I could see it. Because we've got two of Nika's Weapons represented by the Strawhats. But, Nika HAS been depicted with a third weapon, the Spear.
Now, there is a part of me that wonders if Oda has subtly retconned the Spear away. Because we've seen the Chapter 1138 Mural. And in that, we see Nika/Joyboy being very close to the "Ancient Giant"'s Spear. So, "Nika's Spear" may have been a misappropriation of the "Ancient Giant's Spear". Which means, the "Spear" could actually be Ragnir. Who is a hammer. Which is confusing. But, oh well.
But, assuming that Nika/Joyboy actually did have a spear, Usopp fits pretty nicely.
Zoro is "The Sword that can cut anything".
Sanji is "The Shield that can block any attack".
So, in theory, Usopp could be "The Spear that can reach any target". The Spear being about ranged attacks, which would fit a sniper like Usopp. Basically being the equivalent to Gungnir from Norse Myth.
https://en.wikipedia.org/wiki/Gungnir
"The Spear" probably fits Usopp the best out of any of the Strawhats. So, yeah...he probably should be the next in line to get Conqueror's.
But, we'll see what happens. Oda has said that he wants to keep Usopp as the weakest of all the Strawhats. So, we might have to wait until literally everyone else unlocks CoC before we see Usopp's true potential. Or maybe he'll unlock his CoC next chapter, while dealing with Gunko or rematching Imu. It's really hard to predict Oda, sometimes.
As for it being a comedic or serious scene...I imagine it'll probably be a bit of both. Usopp will probably take the moment seriously. It'll probably be a big epic moment of character growth on Usopp's end. But, I could see whoever ends up being on the receiving end of his new CoC-infused attack making a classic Oda reaction face. Just not believing that THIS GUY has CoC.