I have already suggested this as an Idea in-game, but I figure I'll post this here for a little bit of feedback from the rest of the community that I haven't harassed with it yet. (Gives me a chance to figure out the new forums, too, I haven't played with these yet!)
Other Iron Realms games allow designers to have their own personal designs and lack Cartels. Here, we are more Trade-friendly with the ability to learn a trade for just the credit cost of transing it out and without additional credit cost, purchase a Cartel (or two, or twelve if we had the gold and urge), but people can't always shake someone down and have them willing to submit their designs, nor can a person newer to the game afford to get a Cartel for their own use, so here is my suggestion.
At the Mastery of a tradeskill, I suggest the adding of a new ability where an individual becomes able to purchase and make use of a Book of Design.
The owner must tune this book to the trade they are designing for, which will not allow any other trade designs to be placed within, so those who can skillflex must purchase multiple. ("Book of Jewelry Design", or "Book of Bookbinder Design" for example.)
For a cost of a 100k, a designer can pick up their first Book of Design, which can hold 10 designs within. These books can be titled like journals and other books and seen when probed or examined as to ease the confusion of owning multiple. This book will also serve as a catalogue of the designs similar to the CARTEL XYZ CATALOGUE command.
These personal designs are subject to a steeper submission cost, 10,000 or 15,000 gold instead of the 5,000 gold cost for a private cartel design. Once the book has been filled with 10 designs, it cannot hold anymore, and another must be purchased for a credit cost from a the artifact shop, scaling in cost the more books that the designer in question owns.
This will still allow would-be-Designers to get into get into doing so without discouraging the use of cartels for shared designs. Maybe, too, one's personal designs can be given to a cartel's private design catalogue at a cost, but designs from a cartel cannot be put into a personal design book to avoid that one asshat that will inevitably try to steal designs out of spite.