Yes, I read that thread with Goggle translate, which is a bit muddy to understand 100% clearly. I also tired the add-on, and it's cool but left unfinished for now, at least.
But changing all the races to be more unique in such ways as the skin tones, hair style, clothing and transport animals would be an enormous work task with so many images to edit and, no least, even creating new pixel graphics (transport animals, catapults, etc.). Also, there's the risk of changing too much, so that it'd feel too far from the original game. Like, slave market for the Romans seems going a bit too far to me, if only an idea. The OP also seemed to be talking about making the Asians yellowish, but BB already made a colour for them (see the Asian warriors). They're light brown. I don't like changing the original work if it's not needed. But, yes, I know there's no restrictions when creating your own mod. I could make the Africans green if I wanted. I only share my opinion. ;)
The question is, if you change the Africans, would you also have to change all the others races for it to make sense? And if so, is it even feasible? BB obviously took the shortcut. At least, as it is, there's the consistency that it's only certain types of characters that has their style matching the buildings of their race.
Thanks, I see. It's too bad they never finished the work, but at least we know what their intention was.