Maybe the real solution is to just rip out the big shelf across the middle and put in something like this.
Under stairs storage cupboard
Dear Earthlings, (Pictures - Combination google & pinterest ) Now playing : GLEE (Rachel & Finn) - Pretending
Clever Ways to Add Storage Around Staircases
Establish an Efficient Pantry | Convert the space under the staircase into a small room for storing food, paper goods, and extra cooking equipment. Add a door and wrap the three walls with shallow shelves.