LPG Cylinder Vending Machine Design

I need a complete mechanical design package for a vending machine that dispenses medium-sized LPG cylinders (11–20 kg). The machine must securely store multiple cylinders, release one on demand, confirm stock levels in real time, and tie into an electronic payment module... (Budget: $250 - $750 USD, Jobs: 2D Drafting, 3D CAD, 3D Modelling, CAD/CAM, Manufacturing Design, Mechanical Design, Product Design, Solidworks)