You can create crowds now using the "grass" tool and changing the grass texture by a video with your characters. You can create different kinds of "grass" with your characters and "plant" them over the terrain. From a far view looks very convincend. Also, you can use popvideos to create HD animated billboards that can be scattered all around the scene.
That is a good idea. And after all, we already have automatic WASD and directional moves - that is all you need for a 3DSMax-like crowd movement. Get the crowd in view at 45 degrees, draw a couple of circles/shapes/ellipses and add an arrow of direction - there's your animated crowd drift add a longer arrow - they move faster. It would apply to flocking birds as well as buffalo, cattle, cavalry, aircraft ...Real movie scenes have a thousand extras.
Crowd / Swarming simulation features would be a fantastic addition to iClone.