no prob, the shader will only draw the lines for triangles in the mesh unfortunaley.

there are a few ways you can get that quad look though.

1. the most obvious is build the mesh to look that way i.e. model the outlines by hand or available tools in your modeler, takes abit of modelling skill though.

or

2. build your model as quads, create uv's for it and do a screen capture of the uv layout before you triangulate the mesh. then make a texture out of the screen capture. and use that as the texture for your mesh.

that all I can think of. I used method 1 for certain debug visual in my engine where triangles just looked too messy, but they where simple  models and wouldn't be as easy ans option 2 on a complex model.

hope it helps some.

looks good Tin, also if you are useing custom shaders you can make double sided with cullmode=none; in the technique like
technique Skinning
{
   pass p0
   {
      VertexShader = (vsArray[boneCount]);
      PixelShader = compile ps_1_1 PixScene();
      FillMode = wireframe;
      cullmode = none;
   }
}