I understand that the provisions OTL make it ASB and would require changed on multiple occasions for this to be feasible.
For starters, perhaps Hitler is much less paranoid of the Army and loosened the leash he has. Enough for them to act with a bit more independence.
To be Frank, it would take a lot of looking into to say exactly how different things would have to be for Germany to have enough men, resources, etc to mount a successul offensive to knock the allies out in the Battle of the Bulge.
My overall question is, should Germany had succeded, what is the feasabity of Germany holding the Russians off and maybe changing the mind of the allies from total unconditional surrender to a peace agreement; which seemed to be Hitler's idea for the operation.