meeters should
not have a great big wide river dividing the map, especially one with no bridges. The AI will be totally confused as it has no routes to some of the V-hexes unless it has a couple of amphibious vehicles, as it only buys barge carriers and rafts as the assaulter if there is a wide river.
The choice of such a custom map is up to the human - so simply don't do that in a non-assault game and all will be fine. Same goes for a beach map (unless you like the thought of all the AI forces drowning in turn 1
).
Andy