Humans use tools.
If you start with the premise that your creatures are humans, you can have them use tools to extend their phenotype such that it accomodates their diet. Humans living on hard seeds and nuts don't need horse teeth. They can use tools to crush up the seeds. Humans living on marrow don't need hyena jaws. They can use tools to crush up the bones.
The hypothesis also suggests that if our early human ancestors
scavenged marrow from carcasses, they would have used tools different
from those used in the procurement of meat. Unlike slicing meat off a
bone, which requires sharp cutting tools, obtaining marrow requires
nothing more complicated than a heavy rock for pulverizing and
It is not as cool as having phenotypically freaky humans with hyena mouths. If you want your hypercarnivore humans to look more carnivory, go ahead and make them that way.
I have to think that a good adaptation to a hypercarnivore diet humans would be hypercooperativity to take down big prey. Humans already excel at that but you could make them better.