Lopess has many small civilizations in the Endovelico mod. Could two people somehow combine them? I find many civilizations in the original game too powerful to be vassals. Also, I think vassals should have territory, perhaps the same color as the empire but with a certain separation. They should also build houses and structures, and have a small economy. I've seen many vassal attacks that are simply overwhelming, not reflecting their true potential. I've observed vassal forces often finish off opponents in battles, not the empire. Besides that, a resource tribute mechanism would be very interesting. You could set a certain percentage and a tribute schedule, and vassals would periodically pay tribute to the empire that controls them. Those are my ideas. What do you think?

That's a good question... I think they potentially would take teh same amount of dmg BUT your attackign unit would not really take any dmg because the unit is facing the wrong direction.  However, I think we would REALLY need to slow down the "turn" speed or something... and that could throw other things out of walk.   But I do like the strategic/historical aspect about trying to ambush, out flank etc.

Pathing clearance is determined in the UnitMotion component, I believe, with PassabilityClass. There are a couple of standard sizes. The bigger the passability class the more problematic the pathing performance. 

It would be so cool if the Minoan priestess could wave snakes around. 

Maybe both, but the Tachara is the Achaemenids' major "fancy" special building.