Hi Derek, SMIRF currently is designed to cover 8x8 and 10x8 variants, which
somehow compatibly are including traditional chess as a sort of superset.
Nonetheless SMIRF has included some additional features like supporting
some different kinds of castling or the absence of Chancellors in Janus
Chess.
Thus supporting more piece types actually is not intended. Nevertheless it
is thinkable to double the supported gaits from 8 piece types to 16 in a
follow-up version of SMIRF. But this will not be in the nearest future.
P.S.: not to forget: the future of SMIRF depends on voluntary donations.