I think that Will's transformation is a significant aspect of the story that Brighouse presents. Will starts off as a dullard who has specific talent. However, he lacks the ability to envision what he can be from the condition that he is. Over time, his change is significant because it shows him being an agent of change. He is able to embrace what can be from the condition of what is. Will's growth and transformation enables him to tower over Hobson at the drama's end. His growth and dynamic condition repudiates the very idea of "Hobson's Choice" as being a condition where individuals are locked into a position of not having a choice. Will does, and acts upon it.
However, I don't think that this transformation is only limited to Will. Maggie demonstrates a particular will within her to simply not be defined by external reality. Age, social convention, as well as her father's labeling her as a "spinster" do not deter her. She acts on her steely resolve and enhances it, demonstrating her own transformation from an elder daughter to an individual force of self- definition. In this light, the story of Hobson's Choice is as much one of Maggie's growth and evolution into what she can be from the external ruins of what is. Maggie herself rejects the very idea of "Hobson's Choice" through her growth and evolution, embodied in the way she drives Will to become a force that he himself never quite envisioned. Granted, Maggie had an independent spirit within her. Yet, it never gains wings and growth as much as it does when she is forced to be on her own in rejection of her father. The driving force of the drama's narrative is as much her growth and vision as it is Will's transformation, something that only happens because of Maggie.