I've played on quite a few maps with rivers/mountains as impassable borders except at certain crossings, and this always kind of irritated me. You can cross rivers, it's just hard and dangerous to do so. So, would it be possible to make a map that makes rivers reduce your offense somehow? Lower the number of dice you're allowed to roll, give defense an extra die, something.
If this is impossible or just a stupid idea, let me know. I'm not the most experienced CC'er, obviously, and I'm really just seeing if this is a viable concept.