There might be a potential to explore this idea without shipping it over to the Ideas for Skyrim section.
I think it'd be impossible to knock someone out with a sword, axe or any sharp object...
A blunt instrument would make more sense, but I feel like theres a greater chance of them being killed too.
Hand to hand is probably the best way to implement it. In Morrowind, it was possible to temporarily knock someone out...but only for a few seconds until they got back up. Its during this time you could continue to wail on them until they died.
The same mechanics could be used in Skyrim, but instead of having a short duration it could be a permanent knockout. i'd see it as a somewhat passive approach to killing.