In a medium mixing bowl, beat together the pumpkin puree, cream cheese, brown sugar and pumpkin pie spice. In a separate bowl, beat the heavy cream with the granulated sugar and vanilla to medium peaks. Fold three-quarters of the whipped cream into the pumpkin mixture.
To assemble: In a small bowl, combine the tea with the orange juice and spiced rum if using. Slice the ladyfingers in half. Dip 2 ladyfingers halves into the tea mixture and place in a single layer on the bottom of a dessert glass. Top with about 1/4 cup of the pumpkin mixture. Repeat with another layer of soaked ladyfingers and another layer of the pumpkin mixture. Top with a dollop of whipped cream. Repeat with the remaining glasses and ingredients. Place in the refrigerator until ready to serve. Just be for you serve, garnish each tiramisu with 2 ladyfinger halves.