Magneto-optical spectroscopy in combination with tunable laser excitation spectroscopy is employed to carry out a detailed study of spin alignment and spin injection in II-VI wide-bandgap semiconductor heterostructures, aiming at optimization of structural design for nano-scale spintronic applications. The use of tunable excitation is shown to provide a valuable opportunity to monitor separately spin relaxation and spin injection processes in the structures. Efficient spin alignment is achieved by using a diluted magnetic semiconductor (DMS) (a layer of ZnMnSe or a ZnMnSe/CdSe superlattice) as thin as 10 nm. The spin alignment efficiency is shown to depend critically on the ratio between the rates of spin relaxation and spin transport within the DMS layer. This allows the realization of spin alignment and spin switching functions by varying the structural design.