Old post but I stumbled on with great info. I do believe a dual could happen again but not without the right breeding, the right owner, the right trainer. That is a lot of right stuff. I had a 100% field trial dog who could have done both. I had him at an international show and a conformation labrador breeder (her moms show kennel is in all the books) who also had been a professional handler came up to me out of the blue and told me he could finish in the AKC ring. I laughed and said, "You do know he is completely field bred don't you?".
His sire was FC AFC Yellowstone's TNT explosion and his mother was sired by FC AFC Crow River's Malarky's Cougar out of an MD Houston Bitch. I also had one that could have finished in the conformation ring sired by Cougar and out of that same MD Houston bitch. With today's field dogs I can see possibilities in FC AFC Gunstalks Top Shelf Snap Decision if bred to the right dog and FC AFC Suncrest Wild Oats. I think if you took an Oatie daughter with good substance and bred to Snapper you may get something you could work with - now throw a little Cougar in there and you may have something. I was told FC AFC Westwinds Bold Tiger was a very handsome dog and it is interesting that Tiger's full sister is Cougars mother. I heard someplace that a pup sired by Pachange Magnum force finished in the ring in Canada.
Most field dogs these days are too weedy without enough substance. The longer I am into breeding labs the fewer really nice looking field trial dogs I am seeing. It could happen with dedication and thoughtful breeding. You would have to have the right dogs. I have a little field girl here now who is beautiful to me but she is definitely not show.
I am always going back and forth between looks and performance and trying to get both - not an easy thing but I have managed to produce a master hunter show champion. I would love to produce or even see another dual in my life time. The picture below it the pup who could have done both sired by Nitro and out of my Penny. He finished his senior title at 14 months old with no fails and only 3 months of training. He was running masters at 15 months. He had a hip injury as a puppy and I kept doing xrays but when it was marginal at 2 years I didn't want to take the chance and neutered him and sold him as a gundog. It can be done but you would have to pick a talented show dog and keep breeding back to nice looking field dogs - or - find the right field dogs.