I kind of like the idea of a sub culture of using WW1 surplus fighters for duels in the 1920s
I mean like as fascinating rather than morally good
I mean like as fascinating rather than morally good
No WWI, keep the landed gentry in power for longer (South wins the Civil War somehow, British aristocracy adapts to investment as an alternative to real estate assets and refuses to back down on the House of Lords), and postpone women's rights as long as possible. That might get you started.
Wouldn't work for Britain at least. Duelling pretty much died out in the 19th century for reasons that had nothing to do with the declining power of the aristocracy - basically it was a combination of public opinion changing to see duelling as something fit only for mockery (duelling could survive being notorious, it could not survive being ridiculous) and linked to this an increasing willingness for jurors to convict winning duellists of murder.
For duelling to survive as even a semi-respectable means of dispute resolution in Britain you probably need a POD in the early 19th century.
I do think that the gap between duelists' abilities is greater than a gap between most (plausible) disputants' legal resources. Having the black-letter law on your side is a genuine advantage in a lawsuit, and the contingency fee system levels the playing field financially for some kinds of lawsuits.
If we're talking Code Duello that won't be quite so clear-cut as you think seeing as the challenged party has the right to choose the weapons used. That would level things out considerably if, say, the challenger is hoping for a fencing match and ends up having to go six rounds in the boxing ring and would tamp down a bit on hot-heads trying to solve all their problems with violence.
Another possibility would be a change in societal attitudes to where dueling is more acceptable not due to violence itself being more acceptable but more out of non-lethal dueling becoming seen as more "fair" than resorting to the legal process. Couple this with dueling being opened up to all classes and between all classes and you could get what would be necessary to make that happen although you'd need a change in attitudes and culture for that to happen going back well before the 18th century at the earliest.
I'd considered that, but even giving the challenged party a choice of weapons doesn't level the playing field THAT much. The traits and skills that people need for a violence tend to cluster, even when you give them a choice of pistols, swords, hatchets, firearms, whatever.