Select the top transform of your model, and in the attribute editor, expand the display tab and open up the drawing overrides section. Turn on "enable overrides", and set the display type of the group to "referenced". Provided that no transforms below the top group of your model have their drawing overrides turned on, by setting the model group to referenced, the mesh will be unselectable in the viewport.
If any meshes are still selectable, select each one, open up the attribute editor, and make sure that "enable overrides" is turned off.