I would favour the way of adding the object first before making it a product (instead of first having a product and then getting the object). Reason is that I forsee the possibility to write one standard way of adding a product to the ecommerce installation. Taking the /o approach, you could then link to the "product" directly.
But how would you link permissions with paid items. I could imagine, if your service contract for creating the product stores the object_id you can easily create a permission record of read. Though, would this be enough? Or do we need to define, what permission will be given to a certain object once the product has been paid? And if so, how do you do this. Should there be a link e.g. in the class administration that says "make it a product", linking to a page that enables you to give some description for the product and the permissions that will be granted on the class (or file, or survey or whatever we might come up with).
Last but not least, how much more work would a general approach be vs. a specific one just interfacing classes and e-commerce. And would you be willing to go down that extra mile Caroline ?
