So I've just bought my Ibanez S520 which is amazing by the way.

I'm big into Gothenburg style melodic death metal. This leads me to play in tunings such as C+ standard and B standard.

Until now I've been playing a set bridge les paul copy, using fairly high gauge strings. Something in the realm of 14 - 62 or so.

I'm just curious, in order to get some clarity and semblance of solidity out of my setup, and to do so without absolutely ruining my neck, A) what sort of string gauge should I be looking for? B) Will my neck need a big truss rod adjustment?
Huge adjustment man, you're in baritone guitar territory there. I would think it could do it, but you would definitely have to adjust it big time. My suggestion is to put the string on, adjust the neck fairly straight and let it settle for a few days. After a few day come back and see how much the neck has changed and adjust it to where you like. Keep in mind that the woods takes a while to settle and you will probably have to fine tune it for a few weeks to come.
I don't give a shit if you listen to me or not
Might wanna have a shop do it then since those strings are gonna pull a lot harder that the 9s or 10s that came on it.
I don't give a shit if you listen to me or not