Mike,
I have built a few of these and I am in the wine business full-time. My last job was built into an alcove in a basement. Outside species was solid Birdseye Maple. Inside, the racks and those boxes divided by an "X" shape were built from Mahogany. I have never finished any of these components in any job. I have tried Pine and Redwood. The Pine twisted a bit. The Redwood was as good as Mahogany. I like how Mahog machines.
There is really no benefit to finishing any interior component. In a temp controlled cellar, wood movement is minimal. In an uncontrolled environment, machined pieces are very narrow. Most wine has a tight capsule over the cork so odors likely will not have any effect. I'd even say the finish could create the "mars" you mention due to the friction when removing or replacing a bottle.
Make sure you consider different bottle diameters as marketing continues to evolve toward some really fat bottles. Find out if your customer buys 1.5L and 375ml bottles. You may need to allocate a certain amount of space to these. Full cases can be stored in the individual partitions or those boxes with the X dividers. A standard 750ml bottle can be a Bordeaux bottle or a Burgundy bottle. The latter being much fatter in diameter. Absolutely take some graph paper and draw these to scale. My first job had too tight of tolerances.
In the future, if you are installing a temperature control or humidifier type unit, just follow manufacturers specs. Vapor barrier, etc.
As far as the mars, wine geeks handle their bottles with kid gloves. They do not want to scratch the labels which is basically the only identifiable means of the content. I don't think I sweat that detail.
Most wine geeks seeking a cellar are looking to showcase their treasures and "lay" the product down to improve. That's why they invest in temperature control units. What most don't realize is it is a tall order for any wine to survive, yet alone improve, for 10+ years.
Sorry, no pics. A computer crash a year ago lost most of my work.
Hope that helps