This is my progress for the 42128 C model:
The semi truck unit is finished. It is modeled after the Mercedes Benz Actros. The cabin is different from that in the B model. The trailer is still a bare frame, but this model is so uninspiring to me at the moment that I cant be bothered to finish it. There are no challenges or constraints that I have to overcome in this model, mostly because there's a lot of space, unlike the B model I designed. I think I'll drop it for now and work on another C model idea that makes me feel more enthusiastic about.