This is why Les' solution makes so much sense. You need the extensions to add enough value to the canned solution to make a profit. The prerequisite of owning the extensions used to make the product, immediately puts it into the developer category. The end-user starts with the same financial commitment as the developer. The developer has all the tools necessary to support the product.
The licenses remain the same as the extensions already owned and the ISP would have to make the same financial commitment as the developer. This brings it all back to developer competing with developer.