Uplinker - thanks for the feedback. In terms of being able to get past people from a window seat (or similar) I have had to accept that you'll need to ask the people beside you to unrecline their seats and get up. With the density of seating required for 33 inch seat pitch, there really is no way around that.
I've found that even on United Economy Plus you still need to ask people to move if you want to get out, and you spend far more time in your seat that you do getting in and out of it, so I figure that is one of the insurmountable issues with economy class.
I'm just about to start buying components for a prototype, so fingers crossed it will work as a concept.