Each player have a Royal Sergeant (A pawn that moves and captures forward and diagonally) and basically unlimit amount of Pawns and Pawn variant pieces. Pawn and its variant pieces can move sideways, always jumps two squares (Torpedo) and no promotion. Those dead Sergeants prevent too early attack.
Game of the pawns

Some update:
- More free square, to avoid the toxic tactic when someone is forbidden from dropping a piece because other drop a piece to their side.
- Only 7 pieces for each variant of pawns. Each player would use their pieces more carefully.
I recommend adding promotion to ferz/wazir, and lowering the amount of pawns drastically. Probably 10-20 of each.
Thank for suggesting. I've fix the amount of pawns. I want this variant is for pawns only, so every pieces never can go back after moving forward, and everyone would be more careful with their pawn move.
one thing that is interesting is that if Red just pushes a pawn along the edge of the board, blue can not capture it, same goes for all the players.
That's kind of a bad idea. You'll just get a bunch of pawns stacked up on the side of the board. Also, Noahfavelo brings up a good point. Switch the king to something else, probably an actual king.
Well... I know it would happen, but maybe it would be a feature, not bug
Anyway, I would try my own version, if it work terribly, I would try your suggestion.