Cast modifier: Cylinder cap

Cast modifier, Cylinder type is missing a cap like surface and all vertices in that area are squashed to cylinder wall. the cap surface can be recovered with vertex groups and smooth modifier but only in simple, clean cases. I work with heavy scan meshes, made of triangles (500k tris) that need adjustments in form but keeping the original textures as much as possible. Also sculpting with material on is not an option for high poly meshes. This would simplify a lot our work. Thanks!