It would almost require a Contrib, something "similar" to what I was working on but different. I'm thinking a submit button within the Node Edit screen that says "Convert to Ubercart Product" or something, and that would trigger the Contrib's function which invokes uc_product_insert (I think that's right) which would be similar to cloning a View. Then you can fill out the product-specific things like Shipping, SKU, etc., and save it. That way you'd be keeping the nid the same but now there'd be a row in the products table to associate it, as well as to allow hooking into hook_node_info() (hook_product_info).