Freehold, you've done a great job of articulating how I've been thinking about this.
I think it's a terrible idea to say, "I'm going to eliminate DA from my lines/breed by not breeding any dogs with DA" because it's just not that simple and you just don't know what else you're losing.
BUT, having said that, if it came down to "all else being equal I'm going to choose to breed the dog without DA" I think over a long period of time DA could probably be reduced in a breed without necessarily losing other desirable traits.
It's just that "all else being equal" is sort of a Hypothetical Land scenario. It's probably not something that is going to happen a lot. There are too many variables and too many factors that would have to line up to be "equal". So it's sort of a mental exercise, I guess.