To start, here goes a fictional river crossing with Parthians facing Indo-Greeks.
Parthian river crossing in India c.1AD
Parthians vs Indo-Greeks
Having outmaneuvered the Indo-Greek army of King Strato, a Parthian invasion army under Suren Gondophartes has started a river crossing at two fords. King Strato has sent fast moving forces to delay the Parthians, hopefully giving the Indo-Greeks enough time to deploy the phalanx.

Download link for base FOG (no expansions required): http://depositfiles.com/files/9irmp41vd
Download link for FOG with Rise of Rome expansion: http://depositfiles.com/files/r0el0kw1w
Both armies have the same points, and the battle can be won playing as any side (although it maybe easier to play as the Parthians). I recommend giving some advantage to the AI side.
The Saka Horse Archers (armed with bow and sword) are cavalry units with a strength of 500 men. The other horse archers are LH armed only with bows, and around half of them are superior.
As of patch 1.0.3, the AI will not use the bows of the Saka Horse Archers, Indian Archers or Greek Cavalry units.
Questions, comments, and suggestions are welcome!

Edit: I have removed the "experimental" version of the scenario after reading this post viewtopic.php?p=120863#120863 . I was not aware that custom games could be played online nor that manually edited scenarios could be dangerous, sorry!
Edit2: New version of the scenario, replaces the old version.
Edit3: New version of the scenario, using Rise of Rome's models, and with minor changes to the OOBs of both sides.
Download link (note this version requires Rise of Rome): http://depositfiles.com/files/r0el0kw1w
Edit4: Download links updated on 18th July 2010