This is the most common philosophy I see in all my research. A philosophy I will be going against.....and a philosophy that goes against what you consider to be the 'simple solution':
Adults must understand that the labels children use are not crucial to family success. What is important is that children are given the freedom to choose which labels are most comfortable. For example, don't force them to call a stepparent "mommy" but don't scold them for doing so either. Children need to be granted permission to use whatever term is most fitting (as long as it conveys a basic level of respect). Telling a child, “feel free to call me Sandra if you like” or “when you are at your mother’s house this weekend, it’s okay with me if you call your stepdad ‘Daddy Tom’—it doesn’t hurt my feelings” is a grace gift to children. It relieves them of worrying about your feelings and frees them to love.