The effect of MHD instabilities on the tokamak à configuration variable vertical observer is investigated, through the approach followed in a previous work for the edge localized modes [1]. In this work, the results are extended to configurations with elongation and triangularity compatible with the ITER plasma constraints, and are applied also to sawteeth and oscillations on the q = 2 and q = 3 rational surfaces. In addition, so-called 'infernal'-mode instabilities appearing in reverse-magnetic-shear and low-shear configurations are analysed. Modified vertical observers are constructed such as to minimize the MHD noise propagation for each case, and then applied to the single instability for which each is built to verify the effect of noise propagation in discharges with different modes. The main constraint for the new observer is given to maintain the response to a real vertical displacement event, which is modelled into the observer. The results confirm that the design of a discharge-specific vertical observer, together with the use of fast plasma control actuators, should be sufficient for safely controlling the vertical position of the plasma in ITER and other tokamaks. In addition, while the performance of multi-mode-optimized observers is generally comparable to that of single-mode-optimized ones, for some of the more virulent ideal instabilities in reverse shear it is found that a dedicated observer is preferable for keeping perturbations to a minimum.