When you cross two breeds like this, you don't get one that is an average of the two. For an individual trait, you could get one that is just like a Malamute, just like a Border Collie, or somewhere in the middle. For example, you could get a dog with the reactivity of a border collie, or the steadier temperament of a Malamute. You could get a dog with the strong desire to please of a border collie, or one that is more into their own agenda like a malamute.
Each established breed of dog has a set of characteristics that works together. When you mix them, you can get a bad combination. What if you get a dog with the dominance and hard headedness of a malamute, and the hair trigger reactivity of a border collie? How about a dog with the super high activity level of a border collie, combined with one that is not interested in being obedient? How about a dog that is same-sex aggressive (found in malamutes) with the sensitive reactivity of a border collie? The aggression that can be found in malamutes should NOT be combined with a breed that has a low threshold to trigger.