The runaway electron mitigation coil (REMC) is an asymmetric, in-vessel, passively driven coil that is intended to prevent runaway electron build up by providing a deconfining perturbed magnetic field during a disruption current quench. As the plasma quenches, the REMC circuit is inductively driven to high (100s of kA) current due to the coupling between the plasma and the coil. Previous modelling results show strong potential for an REMC system implemented on SPARC to mitigate runaway electron growth[1, 2], motivating the full design and implementation of the REMC system in SPARC tokamak. This talk will provide an update as to the state of the REMC design implementation and will review various lessons learned in the physical design process. This includes addressing REMC ex-vessel circuit switching needs, protections of sensitive circuit components from neutrons, ex-vessel inductance and resistance limitations, and in-vessel electrical insulation material requirements. This work is supported by Commonwealth Fusion Systems. [1] Tinguely R.A. et al 2021 Modeling the complete prevention of disruption-generated runaway electron beam formation with a passive 3d coil in SPARC Nucl. Fusion 61 124003 [2] Izzo V. A. et al 2022 Runaway electron deconfinement in SPARC and DIII-D by a passive 3D coil Nucl. Fusion 62 096029