I have this thing about Ron — it always infuriated me how unfairly JK treated him in canon. He was always in the shadows — his brothers, Harry, Hermione. After the war, he joined the Aurors just like Harry, but the point is that it was what Harry wanted, not Ron. We never saw Ron wanting something of his own. The Auror department was not his story. Eventually he left after a couple of years and joined George at Weasleys' Wizard Wheezes. Again — not Ron's story. He just joined something existing, something created by others.
So I have this headcanon: what if he accidentally discovered something that didn't exist before, patented it, and hit the jackpot?
Arthur always loved Muggle inventions. Ron didn't mind them like any other Burrow inhabitant — he maybe even cringed at his father's collection of socket plugs and batteries — but deep down, he liked Muggle inventions. It just wasn't about plugs. It was about something grander — cars, planes, washing machines, dishwashers, TVs, computers. He just never exposed it.
What if, at school, he had the one thing that differentiated him from Harry — he attended Arithmancy because he… liked it? Had the required skills and mindset for it? He was brilliant at chess, after all.
So after the war, he joined Harry in the Auror department, left after two years, joined George… and a couple of years later, he accidentally discovered the formula that makes Muggle inventions work in magical houses. He created a tool — a small magnetic button that is placed on a Muggle object, and it works in a magical house.
And it could complete his arc about all his insecurities — being in the shadows and the lack of money.