OK. I've just had the best idea ever! Mr OL, if you're lurking, I want royalties from this.
Instead of seats, how about 3 or 4 beds, (or as I like to call them, coffins) stacked one on top of the other a bit like those pods that the Japanese call hotels for businessmen. You get in through a hole at the aisle end, lie down on a mattress, with a pillow. strap in and enjoy your flight. There would still be a central aisle and beds either side of it.
Remember the film The Fifth Element, when Bruce Willis gets on the spaceship whose interior is a bit like this and they tranquilise him? Then you wouldn't need any cabin crew!
I haven't done the maths, but the beds would have to be angled slightly to fit a 5' 10" long bed in the space normally used for three average seats (just under 5').
People over 5'10" are freaks and should not be flying in the first place!
It would certainly end the envy of economy passengers when they think about the comfy beds that Business and First Class passengers get.
Unfortunately, there could not be a door on the hole at the aisle end as the build-up of Methane could be too dangerous!