Quantum communications have garnered an increasing amount of interest over the last several years. One of the key components, a deterministic single photon source, requires both high quantum efficiency and suitable emission wavelengths, particularly for ubiquitous fiber-based systems. Solid state single photon sources, comprised of a crystal with isolated, optically active defects, are particularly advantageous in terms of their potential for fine control, reproducibility, ease of operation, and scalability. However, random orientation of single defects presents challenges in terms of scalable manufacturing of such sources. In this paper, we numerically demonstrate Mie resonant core–shell structures that are to a large degree insensitive to random impurity dipole orientations and at the same time decouple spurious decay channels by enhancing both absorption and emission rates. Applying the simple core-shell design to Xenon-related color centers in diamond nanocrystals enhances emission rates into the main zero phonon line by a factor of 23 relative to the bulk diamond. Addition of a Bragg-mirror shell to the Mie core-shell permits a great deal of further increase in the enhancement factor: e.g., a factor of 1273 for a two-bilayer Bragg mirror. A great deal of insensitivity to both the emitting dipole orientation and positioning within the nanocrystal was demonstrated.