Custom kernel will get ya there. Can also try this if Knox is truly disabled on your device and it might work with the stock kernel: http://forum.xda-developers.com/show....php?t=2524485
Wanam Xposed also has an option to change to permissive upon boot.
Just a few more options for you.
Ok so I think Im missing something here...
I just flashed http://forum.xda-developers.com/show....php?t=2741086
Downloaded the zip and flashed it with safestrap. Said it worked.
In about phone my kernel version did not change (Thought it would.)
Still cant seem to disable SElinux.