I have been searching the suggestions board as much as I could to see if this had been suggested before, but it has only been briefly mentioned as a small idea once or twice in threads that deal with rather different issues (e.g. a 40d era thread talking about how champions were too easy to get). I have thought about it for a bit and decided that it's best if I just make an actual thread dedicated to this idea.
I was inspired by The Winter King series by Bernard Cornwell, which includes stories of the various ancient British kingdoms having "champions" that could be used to fight another kingdom's champion to solve a dispute without war. It then occurred to me that this could be applied quite well in Dwarf Fortress.
For example, imagine if your international relations have become strained somewhat with an Elven nation near your fortress over their cannibalism and your passion for oak mugs menacing with spikes of teak. This has led to open war, resulting in heavy casualties on both sides. Your diplomat discusses the dispute with the Elven diplomat; they agree that your champion and the Elven champion should both fight to the death in a location of their choosing, which turns out to be woodland. The champions fight long and hard; the elf dancing from tree to tree with his bow and your dwarf hacking through the trunks with his axe to destroy the elf's hiding places. They fight for days. Eventually, the elf is overwhelmed and beheaded, but not before the dwarf is shot with a poisoned arrow. Their bodies are sent home upon their shields and the dispute is solved; no more innocent blood must be spilled. This event will go down in history and will be the stuff of songs and legends for years to come.
You see, right now Champions are more like glorified drill sergeants in that only really instruct dwarves. If champions were meant to be drill instructors, why not just call them instructors? "Champion" doesn't seem right for a soldier like that. This suggestion is just one way in which champions could actually do a job involving "championing" your fortress.