I once watched a terrible d-list syfy movie(it could have been a tv show episode, actually? doesn't really matter) where they said "frozen" instead of "hot" or "cool". For me, it was terribly obnoxious. I would grind my teeth whenever it was used. So, one major reason for this thread is that I don't want the slang to end up like that.
Also, the stories involved do not take place in our universe. So there's the usual problem of the "translation" convention, where the story has to be in english because that is the audience, but they aren't really speaking english. So a lot of slang words and puns and wordplay that would fly in an Earth-based setting aren't going to work here. Unless I were to use the method of "translating" each register into a specific Earth register--a practice that doesn't tend to work for me when I read a story--which would pretty much drain all the whimsy out of the different speech patterns, anyway.
I've run into this issue a lot with fan-subbed anime shows, where the jokes all work in Japanese, but not in English. Don Quixote, I believe, has a similar issue, as do most translated works. A common practice is to insert an English joke/pun as close to the original as possible, or to use a translator's/foot- note to explain. Not a big fan of footnotes in books, either.
I haven't really read any books that involve similar situations, so that's why I was hoping for some recommendations. JW's response is pretty much what I had in mind, but the connections between words in a language other than one's native tongue are just damned hard to get across. Even "Cockney" rhyming slang trips up most people who aren't used to it, so a slang based on an entirely different language is like Everest compared to rhyming slang's indoor climbing wall.
I think if the world is strong enough any slang will sound right.
