Make sure you play an S for a while before you buy one (actually, this should be the rule for any guitar!).
There's something about the S series that just doesn't jive with me, and I'm an Ibanez guy. It's not the thinness, because I also love Parkers. I don't know what it is. Every time I pick up an S it's like "well, this is a nice guitar... but..." And they are
nice guitars; they're just got for me.
Yeah, if you like the thicker necks, the JS
series might be more your thing.
BUT, if you are really wanted a change, you might not want something that is too similar to what you are used to.
Most of the entry/mid range RGs will come with Wizard III necks. The Wizard III isn't super thin, but it's probably thinner than what you're used to, and the radius is much larger so the top of the neck will seem flatter (which is good for technical playing).
The only thing really thinner than a Wizard III you will find will be on the higher end Ibanezes (Wizard Premium, Wizard Prestige, etc.) or on some older, used RGs, which may have the Wizard I which will feel as thin as an iPhone if you used to Fender necks.
Here's a page with some more info about the dimensions of different Ibanez necks and when they were used:
As mentioned, you also may want to check out something with a push/pull coil splitting so you can get even more versatility in your sound, although I don't know of any current Ibanezes off hand that do this (it can be added aftermarket).