Hi, i don't really know what you want to use this for so this might not help, but yes it can be done although it can't be toggled and is a bit awkward to switch between . Basically what you have to do is select the object you want to be wireframe then hit ctrl + A to bring up the Attribute editor and on the shape tab scroll down to Drawing Overrides and check on Enable Overides,then finally turn off shading and that object will be wire frame and still workable but it will still be shaded if you render .
To get back to being shaded simply follow the process again and check shading on.

If you wanted to render with one object as wireframe then i'm afraid you would have to render out two seperate renders ,one with the Software Renderer or Mental Ray for you shaded objects and the other with Vector Renderer for your wireframe object and then composition them together.