In modern developing world, there is a growing significance of the contradiction between versatility and ease of manufacturing. Products should exist in many user-centered variants, that are manufactured with the least resources possible. The purpose of this work was to formulate a novel method of modular design and assessment to improve design of multivariant products that undergo evolution of Main Parameters of Value. The proposed method represents a systematic approach in technical system segmentation, that is one of the 40 inventive principles in TRIZ. It is based on identification of system evolution and optimized selection of modules and connections between them. As a part of the method, a novel modular ideality parameter was defined that quantitatively describes segmentation principle in the scope of increase of the useful function, increasing versatility of a product with no to little harm to ease of manufacturing. This approach makes it possible to design multi-variant products that represent a systematic and structured application of a segmentation principle. The application of the methods was shown on an example of a Mobile Biogas Station. It was shown in the study, that modular ideality has an influence on ease of manufacturing and resources usage of multivariant product design.