He doesn't have the speed or finishing touch to be in the top 6 IMO - Kane is the best option for Eichel's wing and is just as capable of using the body to battle for pucks as Girgensons.
Putting Girgensons as the LW on a line centered by Larsson with Pominville on the other wing for a strong forechecking, 2-way checking line would be my first choice. Larsson and Girgensons had some brief chemistry as linemates in Rochester and both play a strong defensive game, have good faceoff skills and can agitate top lines of opponents. The trio could be as effective as the Foligno-Larsson-Gionta line was, with Girgensons doing what Foligno did and Pominville picking up what Gionta did.
I'm dead-set against any scenario that demotes Larsson to 4th line minutes as he proved that he can handle more responsibilities that that role would limit him to.
A lot of that had to do with the rapport Girgensons had with Nolan, who championed the underdog, us-against-the-world mantra. I think that emotional approach Nolan used with Latvia and the Sabres helped Girgensons overachieve those two years - but he's shown that he's more suited for a two-way checking role than any offensive-minded role IMO.