Hi
Thinking of doing the same thing. Not going right into the lowest part though - am blocking that off in fact, as otherwise things will get thrown in there, never to be seen again. In the high part, the hope is to put a pull out coat rack, along the lines of your kitchen larder pull out press, but deeper. I'm hoping my brother will be able to do this. Hafele have a thing for this, but it's only around 500mm deep. Area for shoes, etc underneath. The rest of the space will probably be common or garden cupboard.
Regards.