Custodian Chess

Setup

Game is played on 7x7 board, without Queen.
There are two possible positions for bishops:

Between knights and rooks, or:

Classically, between King and knights.
In first position bishops can attack the Throne. But in the second they can attack one more square (due odd number of spaces), including corner ones (but in cooperation with rooks only, see below). Yet, I think first position is better.
Bishops on only one color are important because they would not be able to cooperate with each other on differently colored squares.
Alternatively, one can play with four bishops, covering both colors. Bishops are quite weak here. But there are two alternative variants, making bishops stronger.

Rules

King, rooks, bishops and knights move as usual, and both castlings work as King-side (and here King may castle from or through check). Pawns move without capturing as usual – one square straight forward (there is no double step). If capturing, pawn may move either straight or diagonally forward one square. On last rank promotes to rook, bishop or knight.
No piece may move to occupied square, there is no capture by replacement. Capturing is by placing two pieces in certain position adjacent to enemy piece. These positions are different for each pair of pieces. It’s possible to capture more than one piece in turn (cooperating with several different friendly pieces). If you make position, that will result capturing your piece if it would be opponent’s turn, your piece is NOT captured. E.g., you may safely place your piece between enemy rooks.
Capturing with two rooks is exactly as in Tafl games. Two rooks must stand orthogonally-adjacent to enemy piece at opposite sides.

Here “x” is for arbitrary enemy piece.
Way of capturing for two bishops is alike, but they must surround enemy piece diagonally.

Two knights must stand knight-leap-away from each other, one orthogonally-adjacent to enemy piece, another – diagonally-adjacent to it.

If rook captures in cooperation with knight, they must stand orthogonally-adjacent to enemy pieces, but at right angles, not at opposite sides.

Alike rule for capturing with bishop and knight, but in their case, they must stand diagonally-adjacent at right angles.

If capturing with rook and bishop, rook must stand orthogonally-adjacent to enemy piece, and bishop – diagonally adjacent to it, and they must also be adjacent to each other.

These are all possible positions of pairs of pieces in relation to third piece, so King and pawns mimic rook, bishop or knight, depending on situation.

For King, it’s quite simple. When he steps orthogonally, he works as rook, when he steps diagonally, he works as bishop. When another piece is moved to cooperate with King, he works as knight.
Capturing never happens after castling, even if rook is placed in right position.

For pawns, it’s a little more complicated. As was stated before, they moves only one step straight forward without capturing, but if move will result capture, they may move on step forward either orthogonally or diagonally. But for them ways are inverted: when moving diagonally they work as rooks, and when moving orthogonally, they work as bishops.
When another piece is moved to cooperate with pawn, pawn works as a kind of joker: it mimics this piece. So, when you move knight, pawn works as knight, when you move rook, or King orthogonally, or another pawn diagonally, pawn works as rook, and when you move bishop, or King diagonally, or another pawn orthogonally, pawn works as bishop.

There are three possible ways to win. One is to capture enemy King. Another is to move your King to enemy Throne (starting square of opposing King), so that your King can’t be captured on next turn. And the third is two block all opposing pieces, so that they can’t move.
Bare Kings is not draw. In this case, winner is the King, which can reach the enemy Throne first.

Notes

And here is another subvariant, nothing to do with bishops, but making special challenge. Instead of being captured, pieces get recruited. They change sides when two opposing pieces stand in position, that would result capture in normal game. And King can be recruited as well, and it will not end the game: one player will keep playing without King, and another will have two Kings. Player with two Kings will have more chances to occupy enemy Throne, as either King can do it. Player without Kings must recruit at least one to have opportunity to occupy enemy Throne again. Player also loses if he or she have only one piece left, and this piece is not King, because at least two pieces are needed to convert. If player have only King left, he loses if this King is also captured.