One further tweak I'm thinking of making to the rules is to let the Decoy move to an attacked space next to its King. This would increase its attacking ability in the endgame, allowing a King + Decoy vs King game to play like a King + Centaur vs King game. But it would not decrease a player's knowledge about which spaces are attacked around the Decoy, because the King would still be unable to move to any attacked space next to it. By checking where both pieces can move, a player could still tell whether a Decoy move next to its King would be safe.
Another alternative I was considering is that a Decoy could move next to the enemy King. While this would also allow the Decoy to behave like a Centaur in a K+D vs K endgame, it would impair the Decoy's ability to avoid check and to detect the enemy King.
One more alternative I was considering was to allow the Decoy a one-time demotion to a Centaur. This would remove its disinformation sowing and intelligence gathering abilities and give it more attacking power. I even considered the idea of letting most pieces demote to lesser pieces, which could be an effective way to sow some disinformation when a piece is about to be captured, but that's probably going too far.
One further tweak I'm thinking of making to the rules is to let the Decoy move to an attacked space next to its King. This would increase its attacking ability in the endgame, allowing a King + Decoy vs King game to play like a King + Centaur vs King game. But it would not decrease a player's knowledge about which spaces are attacked around the Decoy, because the King would still be unable to move to any attacked space next to it. By checking where both pieces can move, a player could still tell whether a Decoy move next to its King would be safe.
Another alternative I was considering is that a Decoy could move next to the enemy King. While this would also allow the Decoy to behave like a Centaur in a K+D vs K endgame, it would impair the Decoy's ability to avoid check and to detect the enemy King.
One more alternative I was considering was to allow the Decoy a one-time demotion to a Centaur. This would remove its disinformation sowing and intelligence gathering abilities and give it more attacking power. I even considered the idea of letting most pieces demote to lesser pieces, which could be an effective way to sow some disinformation when a piece is about to be captured, but that's probably going too far.