Answer by Kiyaku

Well i think it is not even possible to use more than one MeshRenderer on the same object, same for MeshFilter.

And i think i never see more than one mesh applied to a MeshFilter on any model of mine. If i have several meshes in one Model, it will be seperated into Parents. Then you can just hide the parents if you need to.

For example if you want to make an MMO and customize your model, you could include all kind of jackets into one model. If you then want to display only the "naked" version, just make the parent "naked" visible and everything else invisible (like "robe", "t-shirt", whatever) (just an example, there are probably better solutions).

If this doesn't help, maybe it would help to know what exactly you want to do.

EDIT:

You could use a function lide to to show only the mesh you enter in the "showExcept":

void Start () 
{
    showExcept("mesh1");
}

void showExcept(string meshName)
{
    foreach(Transform temp in transform)
    {
    	if(temp.name == meshName)
    		temp.renderer.enabled = true;
    	else
    		temp.renderer.enabled = false;
    }
}

So in this case, only "mesh1" will be displayed, everything else will be invisible. you could write several function (to activate only one mesh without deactivating the others, activate everything except one, etc).