Lifespan might be an issue for the breed. Both Great Dane and Saint Bernard are short lived dogs; working dogs get a lot of training so a few years lifespan might be a consideration in the “investment.”
Superior dog? Just get the German Shepherd back to what it once was, at least pre-’60s (as usual, the ‘60s ruined everything).
*Ahem*
Only using 2 breeds? How is this really superiorizing for “all traits”? That’s nothing but a simple mix.
2nd of all, are you the ONLY 1 involved in creating this breed? What is “numerous litters”? To see results in a rather short time as claimed for 1 person, it’d have to be a puppy mill! A few litters ain’t going to cut it as far as “conclusive results”. I’d feel better if you claimed to be forming a small club of enthusiasts who all were working together. I fear a puppy mill effect, otherwise. Lots of pups in too short a time is just too difficult to handle nicely (although they look fine).
I also can tell you a big heavy dog will NOT make a good hunter or police dog. It ain’t size, it’s agility.
The superiority of your crossbreed all depends upon what you're breeding for I suppose.
Each to his own.