In-game
Hausser can only appear as a leader if the player plays Reinhard Heydrich's path for Germany and goes down the Burgundian-SS path of Heydrich's focus tree. Of the 3 possible leaders for the Command Staff Waffen-SS (the other two being Herbert Otto Gille and Sylvester Stadler) Hausser is the most loyal to Himmler, and as such, is best dealt with by conquest as opposed to diplomacy.
Trivia
At 81 years old, Hausser is one of the oldest people in the game.