First off thanks to OP for really great info&support on this thread.
Second I just wanted to share one observation:
- rooting with saferoot from mainthread, it was dated for 24.05.2014, done on n7100 with MK9 stock
- after root everything is on official, knox 0x0 etc
What I mean to say somehow I am very lucky or sth, but I didn't even need the additional tinkering with Xposed to keep my phone "Official" on 4.3 MK9. Nothing, just run saferoot and done!
<edit: ok, a few root apps installed, couple of reboots later and now it's showing custom>
Question @cosmyndemeter: what do you mean by flashing MJ5 bootloader in post #205? I mean is it possible to downgrade bootloader like this from MK9 to MJ5 without tripping knox?