I've recently rooted my tf201. Unfortunately I was on JB, so I've had to unlock the bootloader. It's all gone smoothly, and I among other benefits I have remapped some of the keys on the dock, which was one of the reasons for going down this route.

Anyway, I'm using TWRP and I've made a backup with it, but I see on their website that they recommend using AndroidRoot.mobi to make a backup that would make the device brick-proof:

TeamWin Projects - TWRP 2.4 - Asus Transformer Prime | TeamWin

However, this is not possible for tablets on official JB:

http://androidroot.mobi/t3_nvflash/

Is it possible to still get such a backup by downgrading the tablet to stock ICS and getting nvflash that way? I would like to have that lifeline before exploring custom ROMs.