Body I think is S/N.
Mind is T/F – Soft and Hard metal.
Heart is J/P.
ISTJ is starting from a Low Heavenly command center with Si having been indoctrinated certain knowledges as foundation, at 30 Te starts developing.
INFP is starting from a Low Heavenly Command Center with Fi, and at 30 Ne develops.
I-STJ or I-NFP one trains to become The (True) Kings Royal Guard … However not The King Himself.