He wouldn't be the Hubbard we know, but he'd still have the same negative personality. He'd be great as a greedy megachurch pastor. He could fit in well with some of the 60s outreach movements to hippies like the Jesus freaks and such. But LRH would have to have a conversion experience and leave science fiction behind, or at least try and write evangelical science fiction. Not sure what the market for those stories would be back then, since it would probably bash you over the head with Christian themes far more than CS Lewis's SF ever did and thus not be mainstream SF. Plus apparently by the 50s/60s, his fiction was pretty poorly regarded--to quote my father, who read lots of pulp science fiction back then, "they just weren't that good." But then again, maybe it could work like early Christian rock did, although I can't imagine leading a megachurch and finding time to write fiction on the side. But he could always inspire others to follow in his footsteps and make "Christian science fiction" (probably Christian fantasy too) into a very important part of the Christian fiction market.
Yeah, I should have stated that I agree Hubbard would have been more than suited to the job of megachurch pastor, had his life gone down that path.
But I still think it's hard to get him off the sci-fi path. From what I read, he was an incurable bullsh*tter, with a heavy emphasis on telling stories about his alleged past lives on other planets. He wasn't just writing science-fiction, he actually wanted people to believe he had lived it. Space aliens are gonna seem pretty heterodox to most evangelical Christians, and reincarnation, simply out of the question.
re: the hippie outreach thing, Dianetics had been around for about fifteen years before the 60s counterculture got in full swing, so if it follows the same history in the ATL, Hubbard is going to be in his mid-fifties by the Summer Of Love, and pushing 60 by the time the Jesus Freaks really get going. So I'm not sure how much influence all that is gonna have on his Christian church, which would have been well established and defined many years beforehand.
In OTL, is Scientology really considered to be a 60s thing, culturally speaking? Like I say, it predates the counterculture by over a decade, and it's general image is actually pretty square(Hubbard was a suit-and-tie guy who bragged about his war record, and they had those quasi-military messengers). The only real counterculture figure I can think of who was involved in the COS was William S. Burroughs, and he was more of a beatnik than a hippie, and didn't bring in a huge following to the church.