Doing quests with kill on sight high level quest NPCs - where's the limit?

[DoucLangur]

I have been thinking of fixing some factions for my shaman, so I was wondering if it is possible to do a turnin with a level 61 KoS NPC, let's say like this:

- someone charm NPC (I believe charm is capped at level 60?)
- do turnin

alternative:
- invis to NPC
- helper (monk, SK) aggroes NPC
- open trade with NPC
- second helper casts invis on you
- first helper loses aggro with FD
- you finish trade with NPC while invis

Would that work?