I agree. Unlocking new unique races/classes would not only spice up the game for experienced players, but also possibly lower the barrier to entry for newer players, by limiting your options from the get-go.
Bitch class could start with the bitch perk at level 3, but have another major upside, maybe in stats, maybe in a unique perk. Same could aply to all the other "Game Over" classes. (Mare, Kitty, Spider egg-sac, Demon, etc.)