Some ideas that human players can implement to extend Douglas Modern chess. These changes would require chess engines to be updated to play to these rules.

Castling

We could allow castling on the queen’s side, done in the same manner as for castling on the king’s side in regular chess. The diagrams illustrate before-and-after:

becomes

Pawn reverse

It’s curious that the pawn is the only piece restricted to only advancing.

We could allow pawns to walk backwards one square at a time. However all captures can only take place in conventional manner, in forward diagonal direction.

Friendly fire

Another rather radical idea I had was to allow a higher-value piece to “capture” one of its own pieces, replacing it on the same square. For example, consider this:

And now we allow the white knight to capture its own pawn, giving:

This is a rather radical proposal and would probably have to survive intense debate and scrutiny before people accept the idea….