A new scheme dedicated to improving spin-transport characteristics by applying random disorder as a constructive agent is reported. The approach paves the way for the construction of novel systems with a surprising combination of properties, which are either extremely rare or even entirely absent within the known classes of ordered materials: half-metals with no net magnetization and magnetic semiconductors. As a real case example for the applicability of the scheme, it is shown that a series of such materials can be derived from the tetragonal Heusler compound Mn3Ga by substituting Mn with a 3d-transition metal.