Short and simple -
Suggestion: It would be nice to have a small storage warehouse/shed. It would be functionally identical to the warehouse, but would take up less space.
Implementation: 3x3 with half the capacity of the warehouse (or 2x2 with 1/3rd), or both
Justification: Sometimes you only need 1 or 2 item types to be near a production facility, and the warehouse is pretty large and feels very unnecessary.