So, if one moves the river, can this cause pawns to demote when they are
again situated on their own side of the river?
If there is no game courier version likely, has the author tried playing
this with a ZRF or over the board?
I assume that the relative orientation of the palace is constant, i.e., the
edge closest to the opponent always faces the same direction and that the
palace cannot be reoriented, say, rotated through 90° as well as or in lieu
of other movement. I assume from the description of the river's movement
as one step towards oneself or towards the opponent at a time that the
river maintains its orientation and does not rotate through 90° either.
This looks like an interesting variant.