I don't really think it is needed, although I would not really care if it was added.
If anything, since its supposed to be vs. Riders, should probably add +2 to movement cost. Although if Keshik ignore movement cost, that would be Ironic. Maybe have it somehow not connected to terrain, so Keshik can't ignore it? Although I guess the mongols did take over china for a time but still, its just a few tiles. defensive bonus may be appropriate, or even a bonus to cavalry units.