Proper Order to Incorporate Ingredients in Pound Cake
What you're probably looking for is a hybrid between your pound cake and a seperated sponge cake, in which you'd probably want to cream the yolks, butter, and sugar, mix your egg white foam with flour, and then fold the flour/foam into the yolk/butter/egg mixture. My gut says the amount of butter in a pound cake will kill the foam structure of the egg whites immediately, but what the heck... experimenting is always fun. 

Another option would be to make a regular separated sponge cake, and then use melted butter as kind of a soaking liquid like you would with a genoise. Might provide the fluffier, yet super buttery texture you're looking for. You could also just make genoise, but it's certainly not as rich as pound cake.