I think Nasri to the MLS would be interesting. Does have some injury issues (and some attitude issues) but his quality is something the league really hasn't seen yet... atleast at his age (28).
I don't know how he fits into Seattle, though. Nasri is a winger, albeit tucked in. He's not a CAM perse, but one that can play left or right attacking mid. He's a David Silva, Coutinho, Alexi Sanchez/Ozil, Hazard type of "winger".
If he does indeed join, i'd really love to see the Sounders play with two up top and a tight diamond (Dempsey, Nasri and Ivanischitz as the three high midfielders).
Either way... rooting for this one. He's on high wages, as mentioned, so if City want rid (and if they do, why not to their MLS affiliate?) maybe they would take on some of his wages. It's not like they struggle for cash. Just raise gas prices a penny in the Seattle area for a day or so.