You seem to be asking a very good here. I am not a lawyer, however, so this is a subject of exploration for myself also.

First, I’m guessing that by “proprietary self-designed fonts”, what you’re saying here is that you have fonts you designed by your own self, and you want to sell them.

I’m not yet familiar with the way they work, but there may be font houses that accept work and market them. T26 comes to mind. Again, don’t take my word for it, but check them out. If they don’t accept submissions, they may be able to give you advice on how you can.

Thank you for the question, and thank you for an idea for a possible future article!