Usopp’s standalone movie
I believe it would be fantastic if Usopp had his own standalone movie. The movie could depict him saving the day or the crew temporarily separating from him. It would be great to explore his backstory from Syrup Village, potentially involving a relative of Kuro coming after him or Luffy. I think it's important to have a good soundtrack and cool effects.
Even though there is a risk that the movie may not do well, I am confident that people would watch it, despite the fact that Usopp has a polarizing perception among fans. This movie could make up for his lack of focus in the series, giving us a chance to see him in sniper mode and using Observation Haki. Fans would be interested in seeing this unexpected side of Usopp.
The movie could also touch upon the Water 7 arc and his insecurities, and we might even get a Yasopp flashback. It would be a refreshing change, as it wouldn't be focused on the Monster Trio and other One Piece characters, but rather on a deeply flawed character that people very very often criticize, despite being a member of the Mugiwara crew. I sincerely believe he could carry a movie alone, though I may be biased. The potential for this idea is huge, and it would likely generate a lot of interest on social media. Usopp fans would be so happy! I know I may be overly optimistic, but a fan can dream.