Guys like Kessel would not at all fit with this team. The guys they should look at on the top two lines are "off the puck guys" meaning either big bodies to take up space and control the walls (such as last year's edition of Ryan Malone) or good positional scorers with a knack for getting open in dangerous areas and finishing (a la Petr Sykora and the old school Buffalo edition on Satan). From what I've watched of Kessel, he's an "on the puck" player, being at his best when he has it on his stick. Since our top 2 centers are 2 of the best "on the puck" guys alive, playing other guys like that on the top two lines will limit their effectiveness.
Oh, and before anyone chimes in, Hossa was a rare "on/off the puck" hybrid. He was just as good with it as without it. Very few guys like that in the league today.