I was looking into new HDPipeline layered shader and noticed that it support blending only 4 layers by vertex color or texture mask. I dont know details behind Ready at dawn shader blending but they can easily create as much layers as they want. They are using library of basic tiling materials and blend them together for creating complex materials with baking only grayscale masks for layers. This approach allows you to save big amount of texture space and video memory. It also allows you to not worry about the sizes of your meshes and texel density. I think it will be very good alternative for current baked asset pipeline in unity.