We can be fairly certain that unit stacking - or armies, if you insist - will be in Civ3, as IIRC the function already existed in SMAC (I could be wrong...).
As for what the units will do when they move and what they will look like, it's all really only eye candy. Fine graphics and animations are cool, but by no means necessary. I would assume 'tho that Firaxis will include all the goodies you mentioned and more, since SMAC has most of them and Activitoin used something similar in CTP. Gotta keep up with the competition.
The 3 images supplied sofar by Firaxis, however, do not represent what the actual in-game units will look like. They are concept images, and a member of the Civ3 team has confirmed that we will not see them bouncing around the map. Perhaps they will apper in the Civilopedia, who knows.
