There is still a lot of complexity involved to support other forms. You can template everything as "you stroke your [specie_adjective] cock", but that does not get you very far, and will "break" the story in many ways.
For instance, how would the villagers react if you keep showing up as different creatures every week? And a lot of the dialogue with Rhot relates to him reacting to your warm-bloodedness. How would he react if you had a different form, or if you change your form partially through your relationship?
And in order for the transformations to have any meaningful effect to sex scenes Hyao would need to add custom text for all sex scenes to describe how your tail is involved, how the characters react to your furry or scaly skin, and so on. So supporting transformations means that all current and future scenes will require considerably more writing.