Oh right, that's a bit shit then. I get why you've done this more now.

That definetely has been a design decision since the beginning. Either you have all of the DLC installed or you can not build or copy/paste the blocks in question. Mind you, this does not apply to the wrecks of the ships that spawn in the game just fine with the blocks. They serve as "advertisement" - but you cannot copy/paste those either.

I remember not having any problems loading ships without DLC, All of the blocks would spawn. Unless they've changed that as of recent

Yes, you can use them - but the blocks from the DLC will not spawn, making this like a blueprint with mods that you do not have. When it comes to things like conveyors or armouries that are embedded deep in the build, it can get nasty pretty quickly. With the worldfile, all the blocks will spawn and you can redesign it carefully, without "boom" (tm) on all all ends.

Pretty sure that even if you don't have the DLC, you can still load and use blueprints that use DLC can't you?