I think that whe all agree that you've got to make youre own choise in this. Other dogs show's us that it's possible to be the top in all the work. Field trial, bloodtracking and apport.
I do think also that it's better to waite untill the dog is a bitt older to start bloodtracking if you wise to compete at field trials.
I am a field trial judge and a bloodtrack judge. We hunt with shorthair Dachshund, IS and IRWS and we breed them as well. In theory it is right not to introduce a dogs nose with ground scent only. In practise I would say, that a clever and passionate dog will easily learn what to do best. Sure pheasants are running..but a good dog will learn to catch the body scent. Working on blood track with a pointer or setter is irritating for continental breed owners, as they tend to work with high head. This time not searching for body scent, but just not inhaling every bit with the nose close to the ground. If blood is rare and the track is difficult, they will also begin to lower the nose.
My friend started her 10 months old IRWS Lohmann's Basior on bloodtrack test from German Government and he was highly praised by the judges and passed with success. He worked calm (ok), concentrated (that is nice) and ... with a low nose. Fellow judges asked, why that ? I told them that he is too young to do it otherwise. But I have no doubt that next spring he will do just as nice in the fields with high head, looking to get body scent of birds.