Everything stayed functioning after 11c. I only had to reinstall the modded Hotspot tethering (since I'm on unlimited data).
The 12B VZW files are available now. This is what I did to install them:
http://forum.xda-developers.com/showthread.php?p=57397975
OP in that thread has links to download the modem, system, and boot files. The system file is large, so the OP compressed it into a .rar -- you extract system-12c.img from the .rar (I did it on my PC)
autoprime's flash2Modem and flash2System are what I used, from TWRP.
It's recommended to update to twrp 2.8.2.0, at least for the System flash. I flashed Modem from the original Bump TWRP without a problem.
I haven't installed the 12 boot image -- waiting to hear from more people as to whether you can still revert once 12 boot is loaded. I'm using the 11C boot, no issue.