When I first started getting into custom knives, I met an ABS master smith by the name of Robbie Hudson at the Guild Show in Orlando in the early 90's. He was a protege of Bill Moran and was known for stuff like extremely complex multi bar damascus Viking and Persian style daggers and big sweeping profile bowies. One some of his damascus blades, the edges were a flame pattern and quite shiny. I wondered for a number of years how he did that and when I actually started making knives, one of the other makers told me that he would draw those patterns on the edge with some kind of resist like nail polish and when the damascus was etched, the edge would stay flat and mirror polished. Some guys do that today to make high relief designs on the blade and others put resist on their makers mark like I do with my new mark so it stays shiny and legible. That would be the easiest way to do what you are talking about and you could choose the shape of the tranistion between the etched and unetched parts of the blade.
"God sends meat and the devil sends cooks." - Thomas Deloney