I will analyze this more later. For now I will say that I am not terribly concerned about piece interaction later down the board. The board is so crowded that such pieces will be traded and dropped long before they get to the end of the board. I am most interested in friendly interactions in the beginning of the game, before exchanges have occurred. I probably like your first suggestion best for now, yes, better than the first few pieces I suggested. So for now, the tentative setup should be:

k
c
-
-
gc
rs
-
gs
l
kn
n
-
p
-
-
-
-
-
P
-
N
Kn
L
Gs
-
RS
GC
-
-
C
K

31 squares total. I forgot to mention, I am considering a different promotion value for the knight: the cavalryman from Ko Shogi. I don't care much for this variant, and it doesn't even really come off as a shogi variant much. But it technically is, and the piece is worthwhile. It moves just like the knight of Western chess. Though there is technically no perfect conversion for the horizontal-ish moves in 1D (as I had defined for the diagonal and orthogonally forward/backward moves), it seems to make sense to me that the sideways moves would translate to a step forward or a step backward. If you think about it, if a knight made a sidways move, then was slide straight back onto its original file, it would be either one step ahead or behind its starting point, and on the opposite color as well. That's my logic. This means that the promoted piece would step one forward or backward, or jump to the third forward or backward. It's obviously much more powerful, but the heavenly horse is a pretty weak promotion, so I'm wondering if that would be better. Thoughts? If we're agreed on all things here, we can probably start a game, and you may go first if you like.