Electromechanics with micromachined vacuum gap capacitors have brought optomechanical techniques to the palm of our hand. Cooling these devices down to the millikelvin regime forms the basis for developing quantum memories and allows us to delve into basic science experiments. To date, only aluminium has been used as device material, and the design has not evolved significantly since it was introduced. Even more, the potential provided by the integration of sensing capabilities was not in the focus of any application driven developments so far. Here, we present several improvements comprising of niobium as base material, a double electrical cavity design and integrated piezoelectric actuators, creating a platform for sensing. We achieve a vacuum optomechanical coupling rate of g₀/2π = 160 Hz, which can be employed for back-action evading techniques and mechanical noise squeezing of the first mechanical mode. We show coupling between the two electrical cavities and the first four mechanical eigenmodes. Furthermore, using the piezoelectric actuator for phononic pumping, we investigate coupling between the mechanical modes among each other. Based on these achievements, it is strongly believed that more research activities will be stimulated in the field of quantum sensing for up to now unexplored and unprecedented application scenarios.