A houzz contributor, not too long ago, had made a wine rack out of 4'x4' wooden pallets, that are used in the US to move a load of goods with a fork-lift truck. Perhaps they have them in your country. He cut them in half so they were only two feet deep and stacked them up to high counter height. The wood would be a nice contrast with your concrete, might add a little warmth to the space. cascio.offsite@gmail.com

You should contact a staircase contractor to provide info and pricing for this cantilever stair design. http://www.caliperstudio.com/fabrication/project-types/stairs/stone-cantilever-stair

It depends on the overall theme of your house and if there are any special requirements for either marble or wood. Wood is softer to tread on than Marble and Marble is easier to clean.

Sir, Its gonna cost a bomb now. There a few space saving options like spiral stairs, ribbon stairs and ladder stairs. Another option which wouldn't save much area but still open up the space is open ledge stairs . Thanks, Amit CORNERSTONE DESIGNS Bangalore