Most of what you'll get will be personal opinions I think. I feel that when you start breeding for something over-the-top and extreme, you begin to risk losing balance by compromising things in other areas. I think breeding, especially with the variety of lines in this breed, will always produce different dogs with different drives, thresholds, nerve, biddibility, etc, all of which can be used to balance out any dog you feel needs to produce less or more of something. To actually go out and breed for extreme anything, I suspect you'll start running into deficits that crop up in other areas. Maybe this is everyones problem with specialty breeders, such as those who breed strictly for sport. Sure they're show stoppers on the field but what about when you bring that animal home and ask it to live its life as a companion animal.
My dog is high drive, has good nerve, grips, downs at the articles, pays attention when i say Fuss, and generally does what I ask her to do. She doesn't chomp down on the sleeve like a monster, she doesn't track like a robot, and she doesn't sail through the air on the long bite... But she very versatile, and I know I can take her off the schutzhund field and into any holiday family function, downtown parade, or just hang with her at the house and not even think twice of "is this a good idea, will she be ok?". There's a lot of value in that for me.