Hmm how about adding some "fords/paths" into code that AI could locate couple into map? Ok, I know that all world's rivers not necessary have them but as random factor by times?
And to Marek: I know that it's realistic but it's quite frustrating to notice that all your tanks are unable to cross river if you have not thought/remembered to add barge carriers into your arsenal... And especially if you don't come to think which tanks/APC's are meant for driving in water too. As I said, river crossings seem to be quite "rare" in campaigns (especially as 1st battle), "land" battles are more common. If AI could choose river crossings as 2nd/3rd etc. battle, player could have "time" to take barges for later use
... And some kind of announcement/warning could be nice anyway.