He desperately needs to learn future sight for Van Auger but also armament haki and having a way to fight in close range/melee as a backup.
Oda nerfed his muscular gains after the TS to make him frail again now which is really disappointing.
I wanna see him utilise Ragnir somehow and maybe that strange Elbaf paint too. This stuff:
https://onepiece.fandom.com/wiki/Painter
But I think also since we've never had a SH eat a devil fruit, Usopp should get one here or a Zoan for his Kabuto somehow but I'd prefer Usopp to get a DF directly.
He desperately needs a powerup and Oda abandoning his observation haki unlocking and amazing sniping has been extremely disappointing. He barely feels like a character anymore too never mind a fighter too.
He's yet to have an actual fight directly that he actually wins post TS except that fishman I guess. Same with Brook. Sigh.
I do think he should use a gun vs Auger as a tribute to his father especially if yasopp dies to Auger.
I could envision scenarios where he would use a gun and why but I definitely can't see Oda doing it and thus allowing it to happen and therefore it would upset a lot of fans and be called too out of character and extreme I guess.