Admittedly, this is not a concept with broad mainstream appeal. It sits firmly in the realm of "comfort fantasy" for those who enjoy macrophilia or extreme size dynamics. However, as a world-building exercise, it holds water. It creates a society where human notions of war, conflict, and politics are rendered obsolete because the hierarchy is strictly vertical. You cannot fight a war when your "waifu" can simply pick up the battlefield and move it.
Originating from the Japanese pronunciation of "wife," a "waifu" in modern fandom refers to a fictional character one has deep, sincere affection for—a paragon of comfort, loyalty, and idealized love. In the secular world, waifus are a coping mechanism for loneliness. In Heaven, they become the reward for a life lived without intimacy. Everyone Has Giantess Angel Waifus in Heaven