I live in Central Michigan and want to create a She Shed in the woods by a pond. The shed was built by the Amish and has pressure-treated timbers under the base, and a weather-appropriate 3/4" plywood floor. It will not be kept heated 24/7 in the winter, but could get pretty hot in the summer and won't have A/C. It would be nice to put a flooring in which will look nice for several years, but which won't peel, discolor, split or have moisture issues from snow getting in between the concrete slab and subfloor. Would bamboo, cork or an engineered hardwood be a decent product for the project? What can I use that isn't industrial...?? Natural materials preferable.
Because you have such extremes in temperature and the potential for moisture, I wouldn't use a man-made material like engineered or laminate flooring. Frankly, I think solid wood would be your best choice. Mankind has been using wood for flooring long before the advent of central heat and it's still used outside the home. Skip any kind of "indoor" finish and use either a porch paint or a deck stain.