Reverse language function. I think that's how it would be called... :P

Maybe a way to get other languages (elves, dwarven, etc.) translated, would be very good, it could even allow to make some books at that language, and you yourself being able to translate the books.   

This is already in place.  Language books can be found in game and maybe if you ask certain people they may have book.
The trick is you have to know one language to know another.  The langugae combos vary. You may need know drow to learn animal lets say.
So planning what extra languages you would like a must as there is a limit to what you can acquire.  Some might say why does so and so speak such and such when they may not be of the race or it seems like they should not.

A character speaking a language one may concider outside the box for them well.  Learning a language could have been for an exchange for a job done or they happened to find a book.

Now I am not sure on this part and maybe Oda or a dm can clarify, but lets say you may have a language you really did not want but are at the max and desire another more fitting , maybe the dm can swap them out with either a good ooc reason or maybe you would have to rp why.

Well, dunno but, what I meant was, "Urzhnak (?) Thrh'rh (?), the dwarven lands, it means Howling Spur, the reason why I discovered the translation was that Grace told me so, otherwise, I don't know how I would get the translation for that.   

Ah that's different.

Trying to think of how this world work...

How the languages work is pretty simple, each letter has a value (Eg, A= Ir, B= Th, T= K, so Bat would become Thirk). In that way it would be possible to make a 'reverse dwarven' language by making another code (Eg, Ir= A, Th =B, K=T), but I'm not entirely certain if the code can handle multiple letters (Like Th=b).

I can see how this might be interesting.

I think what Hacatsu was talking about was not just a book teaching a language, but rather a book written in the language. Let's say the dwarves wanted to write books for each other, and didn't want non dwarves getting a hold of the secrets- write it in dwarven. That's all well and good, but we as players can't understand dwarven. We'd need some way to make the book readable to us. A widget that translate it back into 'common' would be handy.

It would also mean that should we come across elven/dwarven/so on place names, we can figure out what they mean. (ODA told me about the Howling Spur XD)

And trying to work out the code yourself is a bit risky, as it'd be tempting to use that meta knowledge when listening to that language with a char who doesn't speak it (Although it would take ridiculously long if your not a genius (And if you're dyslexic))

A script like this sounds complicated to me, but I'm not a scripter in any sense.

As it is, there might have to be other ways around this: listing the coded words used in game, or maybe having it that the 'dwarven' books are only available to be taken out of the library (when that function is fixed) by people with the dwarven language widget.

*nods at what Elgate's saying* You got it, that's exacly what I meant   , and indeed, I'm no scripter, but that does look like a complicated one, but *shrugs* we got the queen of scripting anyway so...