It would be really cool to apply this technique to trees as well—having elephants walk past them, shaking or even knocking them down, or catapults toppling trees when they fire. That would add a great sense of realism.

Maybe it would be nice to have some custom scenario with all put in place to test everything (elephants going around tight spaces, them and cavalry charging infantry, ship collisions, etc), while knowing what the idea for each should be. Then we can compare different implementations in many particular situations.

@real_tabasco_sauce there is nothing that force elephants or boats to be "solids". Above you have videos of cavalry charging some civilians, you can see it's still doing some physics, but if you don't add "solids" to boats and elephants :  1. Their collision area is a circle at its center, so things that hit him and that he hit  don't spin him as much as you'll expect have to hit him at center, front and back are ghost parts you can just go through are weaker (elastic) 2. Path-finding don't ignore idle units so they are considered as obstacles

Well apparently this thread is already about trying to get units that both try to not overlap, and still manage to move around in groups of 50 without too much weird stuff happening... 

Written down in their present form in the High Middle Ages. Even if they refer to supposed events from a millennium earlier, it's hard to know by then what external influences and other anachronisms could have crept in in the story (as I've recently mentioned happens with funerary practices in the Iliad, where half that time passed).