I kinda get where Eranok is coming from. Make it so that any blueprint you design, you have infinite of, but to give it to another player you sell them a one time use item. But then as a player buying a ship, I might as well buy a premade ship rather than a blueprint.
I'd suggest making it so a purchased blueprint has unlimited use, but can't be transferred again. That way, only the original designer can sell the blueprint.
So original designer can sell as many copies of the blueprint as they want.
Player buying the blueprint can use it as many times as they want, but they can't sell it.
This doesn't stop people from reverse engineering the blueprint, and then being able to sell it, but short of a plagiarism checking system, I'm not sure how you could stop that.
Although, a plagiarism checker with this system only needs to check your 'original' blueprints against your purchased blueprints, rather than all of them.
This could still be worked around, but at least makes it a little more difficult.
Another thought for a plagiarism checker would be an in-game blueprint register for commercially available ships. So if you want to sell a design, you have to get it registered to your name. This checks your design against existing designs and flags any that are the same.
This way, people could still make copies of existing blueprints, but they can't openly sell them (cue black-market interactions).
"Plagarism Checker" is not only a terrible idea, its pretty much a non starter from a design standpoint.
First, the most efficient designs are going to tend to be very similar even without two designers looking at one another's ships.
Secondly how do you even define "Plagarism"? An exact copy of a blueprinted ship? okay, I'll move a bolt.
A similar design? What defines "similar" and by how much? What if I move a bolt? What if I move a beam? At what point do you draw the line between a "Copy" and just plain efficient or smart design? You can't.
Why bother in the first place? Why all this talk of protecting blueprints like they contain secret sauce? The design is right there for your customer to look at with their own eyeballs, and that same customer will HAVE to learn your design ovber the course of the ship's life because they're be responsible for maintainence and installing any upgrades they want to add to it.
Blueprints don't exist so you have have a super special one of a kind design. They exist specifically to ENABLE not PREVENT making copies of that design. If you don't want somebody easily copying your design... don't sell it.
Again you're not selling a secret when you're selling blueprints. You're selling labor. The time it took to design it. People are paying you primarily for convenience. They don't want to reverse engineer a design or make their own. They just want a solid ship they can throw resources at. The few people that do reverse engineer and copy your design put in even more labor than you, and exist to prevent you from getting lazy.
In a game with such a large engineering component it is severely anticompetitive to try and basically invent copyright law, and not only that it is virtually impossible to implement or enforce in any meaningful sense. Its a waste of time that serves only to make the game worse.
Competition for your blueprints shouldn't revolve around a system that prevents competition and encourages you to just sit on designs. It should revolve around constant iteration and innovation of the ship designs.
People shouldn't be forced to buy your design just because you signed a paper that says "OC DO NOT STEAL"
They should want to buy your design because its a better design than theirs, and a better design than the last one they bought from you.
"Limited Use" blueprints assumes there is a way to tell when a blueprint is "used"
There isn't. This isn't EVE where you put a blueprint in a menu and out pops a ship. Blueprints are holo-skeletons that require a tool to run over them in 3d space. To build a factory you'd need to do a ton of engineering probably more complex than half the ships you were going to build with it. I could get unlimited "uses" of a blueprint by simply automating 99% of the building and finishing the last 1% myself.
This entire conversation seems to have a fundamental minsunderstanding of the whole point of blueprints in a building game.