If you don't want to settle for either colour shade (dark or light) you can always do a mix: frame of your storage light and have the inside of the shelves is dark or the other way round to match your existing furniture. You could even go and make it a great feature wall. Maybe some the images below will give some inspiration. Another option is to "frame" the fire place area by putting some fire safe material behind and under (maybe in the exact height of your black sideboard on the left wall). Storage could be mounted to upper half of the wall. I'd probably try to leave the storage half "open" since the fireplace is kind of freestanding.

we used the IKEA online planning tool to design our storage system at home using Billy and Besta componants and produced plan and 3d views of our ideas and a list of all the necessary componants. At the store we could take our list directly to the self service, select all 19 boxes, load them on two big trolleys, used the same list for easy payment at the checkouts and had everything packed in our ute within 45 mins including a coffee break. Assembly, including arranging and re-arranging to confirm our original design and screwing tall shelves to the wall took about two days..Deciding what is allowed to be placed in our new shelves is an ongoing process but we're happy with a result that we think would be a fraction of the cost of modest custom built cabinetry and is so much more flexible

I know that you only asked about what to do with the wine cupboard, personally I would be spending money on trying to make the entrance into the kitchen from the front entrance much more open and bigger Who ever designed the house went for over kill by adding a wine room and the study/computer room and then not making the most of the WIP & WIL by putting the entry into these to the side instead of centering them using either doors or cavity sliders. I would be looking to reduce or open up some of the study space to allow for a bigger opening into the kitchen/meals/family room, the current door size is crazy. cheers

A good idea would be to write down a list of everything you will be putting In those cupboards and seperate them into items that need to go into the overhead(bulkhead) and into the standard overhead cupboards. Write the minimal space/dimensions that these items will occupy. Ask a designer to do an elevation layout and position glasses/appliances and their minimal spaces on this elevation. That way you can ensure your bulkhead/cupboards/internal shelving is constructed so that no space is wasted. Also you can get feasible installations in overhead cabinets so these items can be accessed without a ladder. They are commonly used for ergonomic design for elderly people. But it could be an option for you if it’s in your budget.