You could use the client.dir variable. It lets you rotate the whole view by multiples of 90 degrees. For example, one player would have the default, client.dir=NORTH, while the other has client.dir=SOUTH to rotate everything 180 degrees.
It rotates everything on the screen using other dirs in their icons, so you'll have to make sure that the cards' rotations are in NORTH and SOUTH in their icons.
Alternatively to above, you could use two seperate Z levels of the map. This comes with the benefit of being able to do whatever you want to one without the other seeing. Not as good a solution as above, thought you might appreciate the alternatives though.
It rotates everything on the screen using other dirs in their icons, so you'll have to make sure that the cards' rotations are in NORTH and SOUTH in their icons.