I agree with this part of your post
Going a bit further, I would really like to see an entire arc in which Luffy practically does not appear, so the rest of the crew have to deal with the villains in the island on their own.
And I don't mean some mini arc with joke villains, like Duval, or just a few minutes to show what is happening with each main character in their own situations, like happened before the time-skip as they got separated.
I mean a serious long arc with a proper villain pirate crew, which could be in Elbaf, for example, and Sanji and Zoro would have to beat the top enemies on their own, without Luffy's help.
I think this would be great because Luffy is always the one who gets by far the most screen time in all arcs, so having one arc in which he doesn't appear would be a nice opportunity for each crew member to shine a lot more than usual, besides having a lot more interactions among themselves.
Just too bad I don't think Oda would have the courage to write an arc without the formula used so far.
I think the arc in which Oda strayed from the formula the most was Punk Hazard, in which Sanji got to fight the strongest opponent in the arc instead of Luffy, though Law was the one who finished the job of actually defeating Vergo, while Luffy just fought the second strongest opponent. This was already nice to see, but it was just one exception, and Caesar Clown was still the main villain of the arc despite not being the strongest.