You need to root in order to do so. (I don't know if KingRoot works on the December update, though.)
From there, if you could make a zip of /system and back up the boot image (I need to double check partition numbers, then I'll put instructions), and post them, someone else could make them into a flashable zip (assuming no other partitions changed much).
Thanks in advance for any help you can give.
EDIT: To back up the boot image, either start up an ADB shell or a terminal emulator on the device, and run "dd if=/dev/block/mmcblk0p13 of=/sdcard/boot.img". The backup will be the file '/sdcard/boot.img'. (Both methods need root.)
EDIT2: Actually, I just realized, once you root, before doing anything else, run "cat /process/mounts", and post the result. This way, we can ensure the partition layout didn't change. I'm not sure if OTAs can do that, but if it did, it might mess things up.