So the door on the left is going to pose a problem as it opens to the wall, this would put the cabinets/shelves off center. This might be okay since the valance on balcony wall extends over. It seems too that they would need to be a shallow profile so that you could preserve the flow to and from the balcony (not hit them with objects or elbows). Could you tape out on the floor, then measure the maximum distance that the cabinets/shelves could extend without hitting them? Leave the tape and practice walking by with out stepping on the tape, see what that feels like. I think that you may have to settle for shallow shelves. I would lower and replace the light fixture to about where the clock is (tape this too for visualization) with something like wall mounted track lighting. (see pic) Are you going to paint as well?

I think this piece is quite lovely. It appears that your couch and chairs have dark wood so I would be tempted to stain or paint the buffet to match these items. Changing the large modern handles to smaller antique ones might help to make it less bulky looking and tie in with the other items in your room.. I like the idea of putting a mirror in the upper door, however much as I like the criss cross effect in the sample pictures, adding more detail may conflict with the curves in your sofa and chairs. You could look for a decorative detail that has more subtle style. As for placement, it might go on the short wall where you have a bench or even on the wall where you have your table with two chairs, one on each side to balance the look.

A combination of Offwhite, Beige Upholstery and dark shades of wood would look good. Provided you keep the wood minimal . The floor can also be a similar shade of wood . Remember whatever you do, make it look rich and elegant, only then will you be able to pull this look off. I am assuming the your ceiling is considerably high as well. Paint the walls and ceiling in offwhite shades with only the feature wall grey

The Color of the glass depends upon the user : 01) Generally people prefer for clear glass to solve the purpose of opening. 02) Go for tinted shade films to match the facade , plays with transparencies, Solar reflective films etc. That again with the purpose of opening . General variant available are in shade of blue green. 03) Then comes the tinted colored glass , that have varieties and options in color . can go with several permutations and combinations of colors in one frame itself.