This paper describes the procedure adopted for the selection of an alternative controlled variable to be used for the vertical stabilization of elongated plasmas in the JET Tokamak in the framework of the Plasma Control Upgrade (PCU) activities. The PCU enhancement project, aimed at increasing the capabilities of the Vertical Stabilization (VS) system, explored the possibility of having a valid alternative to the controlled variable ZPDIP used for several years. This study was mainly aimed at improving the VS capabilities by reducing the effect of Edge Localized Modes (ELMs) on the vertical position estimator. An additional motivation was the need of operating JET in future campaigns with the new ITER-Like Wall (ILW), which is expected to significantly shield some magnetic diagnostics. The alternative controlled variable was also planned to play the role of back-up solution in case of troubles with the standard one after the modifications of the radial field circuit. The selection was made paying particular attention to robustness, reliability, and reduced impact on the ongoing experimental campaigns. The new controlled variable, denoted as OBS05, was successfully tested in JET on a variety of plasma scenarios and became the new vertical velocity estimator for VS system.