I think when cooch comes back he should play with the joes. I said it before the season started, and think when cooch comes back is the perfect time to try it out.
Our second line hasn't missed a beat with hertl there, and cooch can ease back into game shape in a slightly lesser importance role as a winger. I think cooch has the skills, and gravitas to not be a third wheel on that line. As everyone has realized part of the reason Thornton doesn't pay much attention to his other winger is because they just really aren't that good, and are mostly there to run around trying to get pucks to Thornton. Thornton has proven he can feed two players, and not play favorites, when he had Marleau and heatley. Cooch is another very good shooter that has chemistry with Thornton from pp time, and years of playing together, even if not on the same line.
So my lines, assuming karlsson is healthy by the time cooch is would be:
Cooch-Thornton-Pavs
Marleau-Hertl-Ward
Nieto-Tierney-Donskoi
Karlsson-Smith-Wingels