In regards to having a construct/ship design and then someone reselling it as their own you need to lock the blueprint design to the original designer and only the originator should be able to make copies of it. However, you would also have to prevent reverse engineering of the construct/ship else someone can just deconstruct it and then build the same item and save as a blueprint with them as the originator. I do like the idea JC mentioned that you can have add-ons to a design (like a mod) to a specific blueprint.
In regards to having a construct/ship design and then someone reselling it as their own you need to lock the blueprint design to the original designer and only the originator should be able to make copies of it. However, you would also have to prevent reverse engineering of the construct/ship else someone can just deconstruct it and then build the same item and save as a blueprint with them as the originator. I do like the idea JC mentioned that you can have add-ons to a design (like a mod) to a specific blueprint.