It's easy with steel to go outside of the realm of easy repairability. In the last days of steel before aluminum became affordable and even before carbon fiber did, it was common to for fancier bikes to have tubing that changed thickness (interior of course) once or twice, as stiffness at the ends of the tubs tends to matter more, and it's easier to weld thicker pieces of metal.

And then you had Serotta, who before they switched to titanium, made steel frames that were not just double-butted, but they also spirally ground the butting to maintain most of the torsional stiffness but lose a couple more ounces of weight.