I can see why, originally, Brambus inventions might have been made so that you can only create one item (ever) because it made you teach someone how to create whatever other items you wanted... thus "spreading" the knowledge. But, a player can be helpful and teach someone to create whatever they want... without having to "use" them to do it.
I don't really see how being able to make all of the contraptions would be "overpowered" especially since you have to know how to make them... (and you could get all the contraptions by having them made) however, if being able to make all of them is considered too much... what about extending the limit to 3?
It would be pretty useful for Merchants... selling such items... maybe Brambus has decided to expand his business, with the coming of Archimus.
I've thought it would be great to play a character that uses all these contraptions (the crazed inventor/mad scientist... something like Doc from Back to the Future 
) and wished I could just make them myself. "shrug"