The problem with a BWB (blended wing body) is that it has problems in meeting the evacuation times required of all commercial aircraft. Put simply, those in the center of the aircraft can't get to an exit fast enough.
Maybe they can counter this with floor / roof exits, but that'll take some convincing of the authorities. Or maybe ejection seats.
Also, those seated at the ends of the wings would experience more up/down motion than those closer to the center.