An excellent find, so thanks for posting. A couple of thoughts from me:

(1) I agree with you that Arneson's Blackmoor clearly had scifi elements therein and was not a "pure" fantasy campaign, so I suppose one could make a "D&D already went there" argument of sorts.

(2) D&D already has scifi elements therein. All of the Barsoom references, of course, plus mention of androids as a direction that a DM might pursue.

(3) I noticed a mention of Gamma World in the article, but I didn't see one about Metamorphosis Alpha (which came first). MA was also a hybrid of a fantasy and scifi campaign, what with the tribes of mutants wandering around with spears and blasters.