The thing I really like about the Franky situation is that it is a dream crashing up against the Straw Hats dream(s) and it's messy. I do get that Usopp was having issues, but I really think the impact is greater because it is Franky and his family beating him up. Better yet, I think the reveal of Franky's flashback and eventually what he purchased with the money make the entire situation into something greater than it was. Also, I'm not so sure it ever gets to the level of drama that it does if Usopp isn't put in that situation and I don't think it can be written the same way if anyone else beats up Franky. Everything about why he beat up Franky, why the money was stolen, and the existence of the Franky Family is an extension of the character Franky. They steal the money for the sake of Franky's dream. You're right that Usopp has to have that moment of truth, even if he's not beaten up, but his relationship with Merry is because of his feelings of inadequacy. Merry is also inadequate for the long journey they're headed toward and Usopp finds a role fixing her, but is also not sufficient to do that. This is the story coalescing into something real and the Shipwright Franky is the most appropriate person to cause it and then fix it.
Does Usopp get to the point of challenging Luffy to a duel if that money isn't stolen (for the sake of Franky's dream) and he isn't beat up? I don't think Usopp's feelings of inadequacy would be so strong if he didn't feel so useless. I certainly don't think he challenges Luffy to a duel, and I don't think the argument escalates to Luffy giving Usopp that ultimatum.
Does Luffy make the decision to get a new ship without that encounter with Franky and co?:
https://youtu.be/pTTFci_e4Ko?t=101
Do we get this moment with Zoro demanding respect if Franky's dream isn't so strong it butts up against everyone else's?:
I really enjoy this stuff, and your mileage may vary, but why I think it wins out in impact even versus a major death is because Oda was able to so beautifully bring it together and make everything connect in the end. As of yet, for me at least, the Pedro sacrifice is like a really good condiment. It added some motivation, but didn't outright change the dynamic of the crew or lead to lasting changes. Pedro seems necessary for getting away from Perospero, but if Perospero isn't there, does anything change? If Pedro is still with them, does anything really change? I don't see it, but I can't imagine Water 7/Enies Lobby and the growth the characters achieved happening without the Franky Family clash with the Straw Hats.