S,
I love your (illuminated-from-inside?) metal-mesh-box-as-walk-in-wardrobe idea on the mezzanine. To make sure there is no other distraction when viewed from below, I propose to do away with balustrades on the mezzanine.
Idea 1:
We can build 1 or 2 long low planters (abt 12" wide x 15" high) from concrete or steel, which I will fill with this lovely plant (what is it called?). They grow to be 3 or 4 feet tall which will act as a more or less effective barrier (no guarantee for the inebriated!).
Idea 2:
Same planters as in Idea 1. And if we can find a good (ie. cheap!) glass workshop, we can build a terrarium glass box-enclosure on top of the planters so that I can grow (or kill) some lovely orchids from Singapore.
Idea 3:
I was very inspired by Tillmann Koehn (http://www.saffroninteriorarts.com/the-artists/tillmann-koehn/), whose house/workshop was featured in the December 2010 issue of House and Garden (UK). He built a lovely steel and glass case which acts as wall divider/display case/bookshelves in his house. I will show you the magazine when we meet on Thursday for lunch. Perhaps we can build a similar one, but much lower and longer. Which I can fill with a few objet d'art.