I was thinking of an interesting plot premise.
The standard arc consists of a buildup, a big battle, and a quick post-battle ending.
Let's turn it on its head.
You come into town, and there's a person who's ruling with fear, based on claims he can direct some force to do his bidding. (think Helmeppo). Now, the Strawhats don't realise this, and just knock him down easily. Everyone panics, thinking of the terrible revenge that the force will do.
The gimmick: the force is long gone, perhaps never did exist. Either it was a powerful being who departed, or a myth. The rule-with-fear bloke has been bluffing for many years.
The Strawhats discover this in a comical way, perhaps during their preparations for the showdown they discover someone who was "defeated" by this force, but in actuality, to keep his image, the ruler did a "witness protection" sort of thing on him, or keeps him in his palace.
In the end, this comes out, and the ruler is deposed. The biggest battle, for a change, is at the start of an arc.