What *I* would particularly like would be a main dining room where the ceilings are perhaps a tad higher, and with excellent acoustics. I know they try, but the dining rooms I've been in on Voyager and Navigator are incredibly noisy.

(I remember fondly the Diamond dining room--despite the sometimes vibration in the stern, it was a stunning room. It had windows on 3 sides as well. Not sure they can manage that design in a new ship.)

I love the sky bar idea, although the bar at the very top of the Paul Gauguin is rarely used except for private functions, at least in my experience.

I've not seen Mariner's observation lounge, but I love Voyager's, and it should definitely have this.