Possible applications of computational molecular-engineering approaches to the design of bistable conformational systems, to be potentially employed in molecular electronics, have been analyzed in isomeric-thermodynamic terms. Constructing such systems led to (conflicting) requirements, viz. an easy interconversion of the two structures (the isomerization equilibrium constant close to unity). At the same time there is a need for both isomers to be sufficiently stable and mutually different (enthalpy-entropy compensation can still ensure the equilibrium-constant requirement). Moreover, the equilibrium criteria have to be necessarily combined with considerations of kinetics. The design problems are illustrated on two model systems: Si6H6 isomeric species and deuterium-and hydrogen-bonded water dimers, HOD . OHD and DOH . OHD, respectively.