The development of new materials using band structure calculations has become increasingly popular due to their resource-efficient nature. However, experimental observations often yield unexpected results, primarily as a consequence of peculiarities in thermodynamic phase formation. As an exemplary case study, we consider the Heusler-like phase Co₂Cr_0.6Fe_0.4Al, which was initially proposed to be a half-metallic ferromagnet; but this composition undergoes phase decomposition due to solid-state immiscibility. Consequently, significant discrepancies have been found between predicted properties and measured values, both in bulk samples and thin films. In the present work, a novel Al-rich composition, Co₂Cr_0.4Fe_0.4Al_1.2, is designed based on prior studies of phase constitution and phase transformations in Co-Cr-Fe-Al and related systems. An in-depth characterization of samples synthesized using the floating zone technique confirms their single-phase nature. We report an unprecedented agreement between properties evaluated by a subsequent band structure calculation using the modified composition as an input parameter and the resulting experimental properties, where, for instance, x-ray magnetic circular dichroism measurements demonstrate significantly enhanced spin and orbital moments without the need for any scaling factor, unlike in reports on Co₂Cr_0.6Fe_0.4Al. Thus, Co₂Cr_0.4Fe_0.4Al_1.2 is a promising thermodynamically stable Heusler-type compound. We, therefore, expect Co₂Cr_0.4Fe_0.4Al_1.2 to exhibit half-metallic ferromagnetic properties. Our material design approach, which assimilates the relevant phase dynamics of the system, constitutes a comprehensive method for future searches and development of materials with targeted properties and is, therefore, of generic interest in a wider set of systems and of relevance to a broader community of material scientists.