Nuclear Visa option abandon
Well, it seems I will never know or need to know the answer to my question on marriage for visa. I was surprised that no one had much to say about it other than the "avoid like a plague" warnings, as it's not that uncommon in, say, New York. In the end it did seem like you'd just open yourself up to complications although a paternity suit would negate someone else's child and a pre-nup would probably limit your exposure legally.
But it turned out there was a more natural path since I intend to live here and do business anyway under the name of my own US company.
I just received word from AFP visa that my application under the "business impresario" category is being accepted by Immigraciones. This came about after dumping birth certificate apostilled, sole proprietorship business bank account, business license and tax return on them and waiting about 4 weeks for "word". It does show that even though the language of the category is geared to big companies or corporations it doesn't rule out little guys. Mushroom farmers from Idaho or igloo builders from Arizona, etc. You too can be a "business impresario" in Argentina.
Of course there's more paperwork that I have to provide, notarized and apostilled and when the local Immigraciones issues the permit here I must then fly back to the US state of residence and formally present the documents to the Argentine consulate who will be the ones actually issuing the visa. Then return to Argentina and what ho, "Bob's your uncle". One year temporary resident visa, renewable annually until they decide to make it permanent.