I wonder if Peyton Manning would be interested at trying his hand as offensive coordinator? The man has essentially functioned as his own coordinator since the mid 2000s. He obviously has a talent for reading defense, and dissecting them. If we could pay him enough money, he could be an asset to the Seahawk offense, and the development of Russell Wilson.
Bobby Engram is also an interesting possibility. McVay himself was once a TE coach. He spent years under Mike Holmgren's system. He is a great WR coach, and he may be a diamond in the rough as an OC given how technical he was as a player.
Matt Hasselbeck could also be an interesting option. During his last stint as a QB with the Colts the fans referred to him as a mini Peyton Manning. He had no arm strength left, no athleticism, no zip, yet he was able to dictate the game and perform arguably better than Andrew Luck that year. How did he do that? By his mastery of the game. He made a bad line look good with his pocket presence, and took control of the offense at the LOS, much like Peyton did his during his career. He also, like Engram played in an offense that featured both finesse, and run it down your throat styles of play.
Other options could be Sean Ryan, QB coach of the Texans. He did a great job with Watson, and if he can implement a similar offense, that would be ideal for Russ.