RB,
If you sign up with the Marco Polo Club, admittedly with a cost of USD50, you can request and most probably be assigned an emergency exit seat. Even when I was at the lowest tier they always gave me an emergency exit seat when I made the request, sometimes several months beore departure.
When you ask for the emergency exit I would suggest aisle since this means you are A)not squeezed between 2 people and B)not sitting right by the door which has the liferaft attached to the bottom, sticking out and cramping your space.