Does anyone know if we will be able to add maybe a box or two on the back of the carriages? This would really help with a character I am Rping as he is a merchant, and this would help with the feeling of transporting goods.

No idea, but I'd lean toward 'probably not' unless something can be done with mods on PC. (Your question seems to imply that characters can actually drive/ride in carriages. Was that in the video? I think I'll watch it again...)

no one know anything until it comes out.