In a food processor, blend cheeses, pudding mix, and sugar substitute until smooth. Gently fold the thawed whipped topping into the cheese mixture. In a separate shallow bowl, combine the coffee-flavored liqueur and espresso. Dip half of the ladyfingers into the espresso mixture until moistened and then line them up along the bottom of a trifle bowl.
Gently spoon half of the cheese mixture over the layer of ladyfingers. Dip the remaining ladyfingers in the espresso mixture until moistened and then line them up on the top of the cheese mixture. Gently spoon the remaining cheese mixture on top of the ladyfingers. Lightly dust the top with cocoa powder and refrigerate for at least 8 hours before serving.