I agree that the lore doesn't really support the idea of multiple house trade lane designs, since Ageira is the only manufacturer. Aeternus told me that it was something he was thinking about for 4.87, though, so I decided to take a stab at it.
EDIT: It doesn't seem outside the realm of possibility that the different houses would commission different designs for their trade lanes, even if Ageira is the only manufacturer of trade lanes. The normal trade lane ingame could be the basic civilian model, and then the houses could have their own personalized designs.