I was wondering if Airbus was going to redesign the bins for the NEO. The 737NG with the Sky Interior wins in practical useable volume for rollaboard bags. By cubic feet, the pivot bins are smaller than the old shelf bins, but are shaped like a rectangle and more useful. I think the A320 really does need them since they have not kept pace with the sky interior bins.
You can say what you want about checked bag fees, and passenger in certain parts of the world bringing too much on board, but larger bins are always preferable for the airlines as they reduce the need to gate check bags and make boarding quicker, which translates to faster turn times.
If you have never designed an airplane part before, let the real designers do the work!