It would be fantastic if embossing would allow you to take a (grayscale) image, define the maximum and minimum emboss / deboss for white (#FFFFFF) and black (#000000) in the image to get different textures and have better control over them. Similar to the displacement mapping feature / trick in Blender.
This would be great for texturizing surfaces or whole objects, making embossing dies / rolls, generate stuff like lithophanes easily, the list goes on.
As for embossing text or sketches, being able to easily add a draft angle to all embossed features at one would be great as well. I imagine that would be immensely helpful for dies and molds where draft angles are necessary for proper release of the material.
On the top of my head I'd immediately use this to texturize partial surface areas of some of my models for better grip (think of knurling tool grips with lines, diamonds, pyramids, dots, or all sorts of different features), generate aforementioned lithophanes for 3D printing gifts, and create various embossing tools, rolls & dies for leatherworking. Maybe generate tiles for tabletop gaming; brick patterns, cobblestone, crater surfaces, various landscapes and such. I'd really, really appreciate this feature, double so if it's not limited to flat surfaces or simple shapes such as cylinders.