Suggestion - Anti-pieces

There is already a variant called Anti-King Chess, but here I'd like to suggest something completely different:

An anti-piece would be an entirely normal chess piece, but not a king, with the exception that the player of one colour owns and controls the opposite-coloured anti-pieces.

Let's assume - for example - that it's White's turn and White has a black anti-knight.

Instead of a normal move, White could:
- Move his (black) anti-knight the way any knight moves, or
- Capture a white piece, or
- Capture another white anti-piece, or
- Capture his own anti-knight with one of his own white pieces.

After any move, he is not allowed to leave his own king in check from his own black anti-knight!

Since one's anti-pieces are immune to attack by the opponent, anti-pieces could be useful for blocking the movement of the opponent's pieces.
Maybe check or capturing could occur as part of combinations.

For example, white to move, black anti-knight on h6 an white anti-knight on b4:

1. ANxf7    Le7 (or any other move)

2. Nxf7#