Question [Q] Nexus 10 back to modified stock?

N10, rooted (supersu), unlocked bootloader, TWRP Touch recovery v2.6.3.1, Omnirom 4.4.2, Franco Kernel R16, ART.

I been flashing a lot, tried many roms... Now looking to go back to stock, but still want to use TWRP, and FK. I'm torn between using xposed (for AppOps and other cherrypicked mods) and Dalvik, or no xposed and ART...

My Question is, what is the best way to get back to stock 4.4.2 KOT49H, while keeping root and custom recovery. Do I need to sideload the factory image, re-root, and re-install custom recovery? Ideally I'm looking for a zip I can just flash along with supersu while keeping the custom recovery. I've looked for a zip file for pure aosp, but all I am finding is the sideload files from google's git, or "pure" AOSP roms with mods....

Also, I feel silly asking this because it seems pretty basic and I probably should already know at this point... The bootloader needs to stay unlocked once a custom recovery is installed, or should I be re-locking? I have been leaving it unlocked, for fear of bricking (aware bricking is not a huge deal with Nexus) but as I understand it, there are security concerns leaving the BL unlocked. Or am I way off base here?

TIA