I'm afraid it's not that easy. Besides, even if it was you'd have to enter things like "59:3b270c58dc0fb4406c0036abeb0b41d4" into the input fields to specify the product "model" for a given attribute variation, and I don't think most customers would be comfortable with that. ;)

Why it's not so easy? Because the function you mention uses md5 encryption (can't be decrypted) on the attribute data to make it unique and so you would need a md5-hash-to-attribute-variation mapping that maps all possible attribute variations to their respective md5 hashes. That's a bad idea though for several obvious reasons. There are better ways of doing it, but it involves too much work for me to do for free anyway and I have no idea how much time it would take. I guess SKU-support would deal with this issue.

Btw, the only thing zen_get_prid() is removing the attribute md5 hash to return the product ID of the base product (without attributes).