I'm a "The Crime and the Glory of Commander Suzdal" man myself. But claiming Smith as a founding figure for transhumanism always strikes me as a bit shaky; he's more of part of the far-future "everything will be different, except maybe human nature" tradition, somewhere between Vance and Wolfe. The Episcopalian element in his work complicates the issue, too.
But I keep meaning to try the research that'd be necessary to do a GURPS write-up of Smith. Anyone whose quirks would apparently include "Values a good argument above anything else - even with his own children" and "Wears a stars-and-stripes glass eye on special occasions" has an interesting character sheet, and he'd drop right into an Atomic Horror campaign as the government advisor who can out-think the weird alien brain. I think he could also appear in pre-war pulp scenarios set in Shanghai, albeit rather young.
As to founding transhumanists - you can push things back or pull them forward as you see fit, but I think that the inter-war bio-tech visionaries like Haldane, the Huxleys, and Bernal may have been the first to really fit the modern pattern (way ahead of the genre SF writers of the period). Julian Huxley seems to have
invented the term, after all, and I've only skimmed Bernal's
The World, The Flesh, and the Devil, but it's a
great source of pull-quotes for TS books. ("The dissimilarity between the conditions of life in space and on the earth would in itself be sufficient to cause perfectly normal, unassisted, evolutionary changes in human beings, but obviously spatial conditions would be more favorable to mechanized than to organic man.")
Which means that transhumanism has Marxist roots, by the way.