Hybrid quantum devices offer a route to combine complementary functionalities of disparate physical systems within a single architecture. Extending this concept to a three-way interface among optical, microwave, and single-spin degrees of freedom is particularly challenging because of the weak magnetic interaction between an individual spin and a microwave photon. Here, we propose a hybrid device architecture that integrates a single diamond color center with a superconducting parallel-plate microwave resonator and a photonic-crystal cavity. The parallel-plate geometry drastically reduces the resonator impedance and enhances the single-spin microwave coupling rate by an order of magnitude. The enhanced interaction allows the optical cavity to be spatially separated from the superconducting structure while retaining appreciable microwave coupling and optical cooperativity above 1. For both NV⁻ and ¹¹⁷SnV⁻ centers, numerical simulations predict microwave coupling rates in the kilohertz range together with optical cooperativity exceeding 1. This architecture provides a promising route toward single-spin microwave-optical hybrid quantum devices enabling functionalities such as pump-free microwave-optical Bell-pair generation.