Single Comment

I really like this game. If a King promotion is desired, perhaps a mW2F2cK
allowing more mobitity with the stipulation that the 2-square move
couldn't cross check (like castling).  This would be worth having as the
promoted King could get out of a dangerous position quicker, but most
mating positions would still be the same.

Let's take a look at promotions:

Knight is a two atom piece that promotes to a five atom piece--this is the
strongest promotion and a good thing -- the 9x9 board weakens the Kinght
vs the Bishop and the stronger promotion rebalances the eqaution.

Bishop is a two atom piece that promotes to a four atom piece, as is the
Camel; the Rook is a three atom piece that promotes to a five atom piece. 
These promotions are of appoximately equal value.

The Silver (FfW) is worth maybe 1 1/3 or so atoms and promotes to a three
atom piece, clearly a a bigger gain than Bishop, Rook, or Camel,  but a
lessar gain than Knight.

The Pawn is harder to evaluate -- it can promote in two steps vs five in
FIDE but does not promote to a decisive piece, so FIDE's 2/3 atom is
probably a good guess.  The Gold (WfF) is worth 1 2/3 atoms, so this is
the weakest promotion--but Pawn promotions collectively can add a lot of
power.