An electro-optic modulator based on hybrid plasmonic micro-ring-disks with submicron radii is designed and rigorously investigated via the finite-element method. The device is based on the conductor-gap-silicon hybrid plasmonic platform and utilizes an embedded electro-optical polymer to control the resonant wavelengths of micro-ring-disk resonators. Such elements combine the easier fabrication of microdisks with the lower capacitance of microring resonators and provide high modulation depths, low insertion losses, and energy consumption around 1 fJ/bit. Finally, an add-drop filter configured in a switching matrix is presented and its performance is preliminary assessed.