Thanks for checking. You actually have two options, the first of which is preferable:
1) Rollback to 3.1.0, install TWRP, unlock bootloader and then flash HDX rom of your choice (presently Nexus v4, CM11, CM12 (two flavors) or FireOS v4). An unlocked bootloader opens the door to a wider array of roms and significantly improved recovery capability should something go wrong.
2) Update to 4.5.2 (via 3.2.6), root, block OTA, install Safestrap followed by either Nexus v4 or CM11. This route is more expeditious but only supports a limited (albeit solid) suite of roms. Be aware once your device advances past 3.2.6 there is no going back.
Regardless, you will need to uninstall Safestrap v3 following the procedure you outlined. I suggest making a backup of your Nexus v2 slot from SS recovery and storing that off-device should you need/want to return to it at future time.
Note that your situation and
@gqukyo's are a bit different as s/he does not have a rollback/unlock option starting from FireOS 3.2.8.
Another user asked a similar question in another forum. I plan to whip up a set if instructions next week. If you can wait that long I'd be happy to include you on the post.