UV Mapping: There's no need that the geometries have the same vertices and uv coordinates, the only that is needed that the face position on the map is the same for one model and other, the eyes position on the map are the same, and so on. It don't matters if you have more vertices or less, they needen't have the same x,y,z coordinates. Remember that the texture coordinates are interpolated between the coordinates of the vertices. For example you can have a plane with a face and 4 vertices or a plane with 100 faces and ~400 vertices, but when you apply a texture they look exactlty the same. Similar dimension doesn't mean that the characters will look the same, you can scale the body parts and do the same with the clothes, apply morphs, different textures, etc

Stupidity also evolves!