not every feature is part of TouchWiz. i found the APKs that i liked using that were supposedly part of it in /system/app. that was how i managed to keep SVoice on a custom ROM on my S3.
Samsung Galaxy Precedent (rooted, AreaRom 3.4 , sd-ext w/ 3.65GB internal space)
Kindle Fire (1st Gen, rooted, AOKP JB 4.1, Nova Launcher)
Samsung Galaxy SIII 4G LTE (rooted, Carbon ROM)