A structuring solution converting starch into a multiphase polymeric material was obtained through a melt compounding sequence, which can be irreversibly shaped by thermoforming into rethinked, sustainable packaging, based on the physical modification of starch with polyvinyl alcohol (PVOH), target fillers, (CaCO3 and wood flour), and a good plasticizer compatible with the polar components. Polymeric material can be thermoformed if it can be stretched without breaking in the positive temperature range, have functional properties required by the application, and keep its shape and properties after stretching for more than six months. The properties of the selected quaternary starch-based compound, fulfil the requirements for a thermoformable polymeric material due to the chemical compatibility between the components and the compounding in a selected procedure and optimal conditions wich ensure a comfortable miscibility. Most likely, the obtained miscibility can be explained only by the arrangement of the wood flour at the interface, where it acts as compatibilizer with a main role in structuring the new starch-based materials. The compatibilizer role of the wood flour was proved for the quaternary selected blend by the changing of the thermal degradation mechanism, from one with two stages for binary and tertiary blends, to one consisting of a single stage: decreasing till elimination of morphological defects, the reproducibility of the mechanical properties, stretching without breaking, and dimensional stability after stretching. Future studies will aim to achieve rethinked packaging for applications that require higher strength properties.