About impregnation types, for now I only plan to add basic impregnation in the next major update. Then, somewhere between v0.4-1.0, I want to make a pregnancy expansion update that could include this (although as a more niche thing it would likely need to be sponsored, because it would require extra work to integrate it with other planned systems, e.g. cross-section view (aka x-ray))
Adding tan lines should be relatively easy. If everything goes smoothly, I might add it shortly after adding clothes