Sometimes it is advantageous for one piece to pass on its horse to an adjacent piece. A magician would have quadruple the mobility and be able to cast spells at a greater distance over a few moves. Also, if the Khan gets demoted to a Khan archer or Khan sword, then that piece could promote itself back to full value by exchanging with an adjacent Warrior, Bondsman or Archer. Of course, the Warrior or Archer gets demoted; such is the price for the exchange.
In long range strategy, it is almost always advantageous to promote a khan back to its highest value rank, which reduces the chance of an easy capture by the enemy. You lose a warrior type piece, which may be crucial in offense or defense, so there is a tradeoff...
In the opening board scenario, there are a variety of exchanges that can take place, provided the 'Exchange' rules is set under Game..Rules
Exchange moves can be made by dragging the piece of interest over one of its own color. In the above example, that would be the white and black magicians and the white and black khans, which can 'borrow' horses from their neighbour to increase their own mobility. (See the blue-circled pieces for white, and the red-circled pieces for black.)
Note: the pieces in question do not change position, they only change piece value, so the following would describe all the possible exchanges:
exchanges
with 
and promotes
to 
and demotes
the exchange piece to 
[E2 to E1] exchanges
with and promotes
to and demotes
the exchange piece to
[E2 to F1] 
exchanges
with 
and promotes
to 
and demotes
the exchange piece to 
[D7 to C8] exchanges
with and promotes
to and demotes
the exchange piece to
[D7 to D8] 
exchanges
with 
and promotes
to 
and demotes
the exchange piece to
[C3 to C2] 
exchanges
with
and promotes to 
and demotes the exchange piece to 
[F6 to E7] Resultant board
If all the black and white magician and khan exchanges moves were made, the board would look like:
