These thoughts have all crossed my mind. The main thing that worries people about PvP is home invasion. Bases take so long to build and fortify that when it is violated players feel the need to wait for the next seed; starting over in moving is daunting and not fun.
Then comes losing their weapons etc. in a fight.
However, there needs to be a risk for PvP, so the toolbar and weapons remain.
You also fail to take into account one setting applies to all... the PvE players as well.I doubt they would want to drop the backpack contents.
Midnight Stranger said it best when he talked about players having empty backpacks because they knew they would lose nothing.
Having zombies walk at night would not encourage PvP; it would only make the game less challenging or not challenging. PvPers do not stress zombies running at night; in fact, I use it to my advantage and do most of positioning at night.