Can you describe what led you to the conclusion "Cannot be projected onto Odoo's product and variant model"? Can you describe the data model of your complex product type?

Of course in principle everything can be projected but in my case (print product) this seems to be difficult or at least not feasible. The reason is that each product exists only once and is, to a larger extend, defined by the customer and consists of several parts. The customer chooses parts and defines their size and the quality, adds own data, and so on. Looking at what I saw this is somewhat similar to what the "Manufacturing" app provides. So let me ask the question in a different way: is the way the "Manufacturing" app does become a product defining app the best way? As can be seen it adds a product instance to its own model.

Please use a meaningful title, your title does absolutely not describe your problem and that's maybe also the reason why you are stuck in the first place. You need some basic ERP know-how to concisely describe your use case and your requirement. Creating an app without knowing exactly what you want to achieve is the wrong way. Creating a new product type does not help either besides the fact that this would be a huge project.