A metal office locker, the kind you can purchase at an office supply store for a couple of hundred dollars. I have added a hasp for a large padlock.
My locker is about 2 meters tall and had five metal shelves, until I removed one to make room for larger camera bags. I can keep cameras and lenses on one shelf, loaded bags on another, my big 4x5 case on the bottom, and boxes of smaller parts and accessories on the top shelf. It's easy to see everything, find what I need, and get to work.
My large collection of camera bags is stored in several places: the most useful are under a work table in the studio, along with my location lighting gear. Less used bags are in a box in the garage. Note that I rarely get rid of a bag -- one cannot have too many camera bags.