I thin WaW2 is possible, and in fact probably the best business move. Lots of grumblings around ghosts and Advanced Warfare. Go back to a game that was successful and critically welcomed with open arms. The war didn't end when the Axis surrendered. Lots of high ranking officials went into hiding, dug in for final stands... There's tons of content that they didn't touch in WaW, that they could go back on. I get where Black Ops was a continuation, but it wasn't direct. You're not opening your mind, I've considered all your ideas. Your one knock is that there is nothing to go off of, and while they can't just go and take missions out of the log, there were tons of battles not represented in WaW. Treyarch could make whatever they did, work.
Imagine this (realistic fiction):
Black Ops: World At War.
Wednesday, May 2nd 1945
Black Ops Briefing, US Outpost. Berlin, Germany.
We can confirm that Hitler has committed suicide. His body has been brought back to the outpost for Autopsy. However, we have confirmed sources stating that the remainder of the Hitler Hierarchy has scrambled to gather all advanced weaponry in their possession, to try and organize a counter strike against the allied forces. Reports have few details, other than a few locations, and that they are in possession of Nuclear weaponry and, Code Name Bell, or as the Nazis refer to it, Die Glocke.
Your mission is to travel the European countryside in search of the remainder of Hitlers forces, end their counter strike, and destroy their weapons. Be prepared for the fight of your life. The Nazis are in a panic, with their leader giving up on life, they feel it is their mission to continue his vision to the very end. However, you have a new, yet familiar enemy. Another nation is in the hunt for the Nazis, not to end their Tyranny, but to gain the weaponry for their own good. The world thinks the war with Germany is over, but the world is still at war.