I'm thinking maybe there should be a configuration in UC saying "Make SKU same as Node id"

I'm confused, why would you want the SKU to be the same as the node id? Since nids are usually numbered incrementally, if you create content other than a product, your SKUs will go out of order once you start switching back and forth.

I do like the idea of having the SKU field pre-populate, but I think it should be based off an earlier SKU value. Maybe there can be a token pattern assigned for such a function. I would also be able to use different SKU patterns for different vocabs or product types. Downloadable content gets "D-###" and Shippable product gets "Prod-##-alpha" or whatever the need is.

I'm making things more complicated, aren't I? I'm good at that.