Make crust: Preheat oven to 350°F. Break gingersnaps into a food processor. Add pecans; chop finely. Add sugar; pulse. Add butter; pulse briefly. Put mixture into a 9- inch pie pan; press bottom and sides evenly. Bake until firm, 8 minutes. Cool on a rack.
Make filling: Sprinkle gelatin on top of 1/4 cup cold water and let stand.
Whisk yolks, pumpkin, brown sugar, cream, spice and salt over medium heat until thick and an instant-read thermometer reads 160°F, about 5 minutes. Remove from heat and whisk in softened gelatin. Scrape into a bowl; refrigerate, occasionally whisking, until mixture cools, about 1 hour.
Beat egg whites with an electric mixer on medium speed until soft peaks form; gradually sprinkle in sugar. Increase speed to high; beat until stiff and shiny. Gently stir a third of whites into pumpkin. Fold in rest of whites completely. Fill pie shell. Refrigerate at least 2 hours. Note: To reduce their risk of foodborne illness, people with health problems, the very young, the elderly and pregnant women may wish to avoid raw eggs.