  This work proposes a methodology to test phenomenologically-motivated
emission processes that account for the flux and polarization distribution and
global structure of the 230 GHz sources imaged by the Event Horizon Telescope
(EHT): Messier (M)87* and Sagittarius (Sgr) A*. We introduce to general
relativistic magnetohydrodynamic (GRMHD) simulations some novel models to
bridge the largely uncertain mechanisms by which high-energy particles in
jet/accretion flow/black hole (JAB) system plasmas attain billion degree
temperatures and emit synchrotron radiation. The "Observing" JAB Systems
methodology then partitions the simulation to apply different parametric models
to regions governed by different plasma physics -- an advance over methods
where one parametrization is used over simulation regions spanning thousands of
gravitational radii from the central supermassive black hole. We present
several classes of viewing-angle dependent morphologies, and highlight
signatures of piecewise modeling and positron effects -- including a MAD/SANE
dichotomy in which polarized maps appear dominated by intrinsic polarization in
the MAD case and by Faraday effects in the SANE case. The library of images
thus produced spans a wide range of morphologies awaiting discovery by the
groundbreaking EHT instrument and its yet more sensitive, higher resolution
next-generation counterpart ngEHT.
