The mention of Scientific Fluxx certainly got me thinking! I think it would have huge educational value and simultaneously be appealing to a great deal of gaming geeks. While we're on the subject, it would be very plausible to make a Chrononauts pack in the same light called "Science & Innovation Pack" or something... what if Edison electricuted himself developing the lightbulb? Flip the "US Implements AC Power Distribution" card. I don't think that that would be a great idea, financially or logistically, but I think a quick survey of Science Fluxx would get some good feedback. Well... I'd buy it. I'm not sure Atheist Fluxx would do so well, especially in the US.
Well, I did consider mentioning Atheist Fluxx but then thought, what's the point? Atheist Fluxx is just vanilla Fluxx. No religious add-ons. ;-)
I know that I'd certainly like a Scientific pack and think it would have tremendous educational potential regardless of whether it was tagged onto the "religion" expansions. You could even specialise in different fields of Science a) catering to specific areas of interest to an individual, and b) allowing for more indepth exploration of each subject. Of course, that depends on how much demand there is for Science Fluxx expansions.
As for religious Fluxx I think that's a matter very much up to the concience of the buyer. I don't have the numbers, but I can only imagine these packs sell better in America because of its high-income low-secularised society. From an idealist point of view it would be nice to have a Fluxx pack for every occasion, even to learn about a religion, but the fact is that diversifying the line to esoteric religious beliefs is not a profitable venture. Maybe a "Religions" pack that contains cards dealing with a wide variety of commonly-held religious belief systems, or even a "Philosophy" pack.
Well, it depends what you count as "esoteric religious beliefs". While something like Bahaism might be considered that (it's most popular country being Bolivia but with only 3% of the population) it would be a mistake to class something like (Zen) Buddhism in there. There is enough popularity in the west that I think it would sell. As much as I'd like to see a Shinto pack alongside a Zen Buddhism pack, the truth is that they would go far better alongside the Japanese language Fluxx.
I don't know about the US, but I know that in the UK there are a fair few gamers classing themselves as "pagan" or at least holding "non-traditional" beliefs that might appreciate cards catering to their world view. And I certainly wouldn't class Hindu and Islam as "esoteric" or fringe religions. ;-)
To be frank about it, the potential for the small boosters are nearly endless to infuse a regular Fluxx deck (or any for that matter) with themes. Fantasy, mythology (mentioned once before), folklore, philosophy (as you suggested), historical eras, various different pop/geek cultures, Cthulhu mythos, etc. Although thinking about it I think just as Zombie Fluxx is getting its own flavour Fluxx I think Cthulhu Fluxx could easily fill an entire deck all too easily.
But I digress, the potential with the booster packs is a fairly costs effective way to inject some customisation into the game for gamers who want to make *their* version of Fluxx a little different without going through the hassle of thinking up their own cards. Just so long as it doesn't become Fluxx CCG. ;-)