Jared,
I would suggest eliminating rules 2, 6 and 7 and rephrasing rule 4 to
conform to the elimination of rule 6.
The bare King rule is unnecessary--if the player has only his King and
nothing in hand he can be checkmated quite easily.
I suggest rewriting rule 1 to allow drops in the fourth zone with these
provisions:
1. You may not promote as you drop (same as Shogi).
2. To promote, you must move the piece you dropped in the fourth zone
within the fourth zone (contrary to Shogi, where you can promote a piece
whose move starts in the promotion zone and ends outside it).
I would also consider eliminating the pawn drop restrictions--definately
the file restriction and possibly the checkmate restriction as well.