Magnetic reconnection inside a Kerr ergosphere can realize a plasma analogue of the Penrose process. An escaping outflow carries positive energy while a counter-rotating branch carries negative energy into the black hole. We study how plasma thermodynamics regulates this process when the upstream magnetic field and rest-mass density are held fixed. The Comisso–Asenjo mechanism is already formulated with the enthalpy magnetization $\so=B_0^2/w_0$. We factor this quantity as $\so=\sigc/\mcF$, where $\sigc=B_0^2/(\rho c^2)$ and $\mcF=w_0/(\rho c^2)$, and follow the thermodynamic loading through the exact energy-at-infinity conditions. We derive the optimal-limit gate $3\sigc/\mcF>1$. Finite Kerr geometry preserves the same trend and heating contracts the allowed spin–radius domain until it closes. The mass-normalized extracted power peaks at finite temperature before closure. In an ultrarelativistic pair plasma, local thermalization self-quenches the channel unless $\chi <3/4$, with $\chi=(p/\rho c^2)/\sigc$. We also derive the corresponding optimal pair-plasma power law and quantify the finite-geometry peak and closure scalings. The formulation yields local diagnostics for GRMHD and general-relativistic particle-in-cell simulations. It provides a direct way to test how heating, radiative cooling, pair loading, and plasma composition regulate reconnection-powered black-hole spin extraction.