Really interesting conversation, thanks for raising this one. I'll throw in my two cents.
I can't see a version of Open where PvP can be toggled off, even if there are many who would like to play that way. IMO, it would go against the spirit of Elite and certainly against the idea of "Dangerous". It's also not easily explained through in-game lore.
However, I do sympathise with those who would like to encounter and interact with other players during their sessions without getting killed. Obviously there are private groups for that, but it's understandably not quite same since you could only meet people you already know.
Overall, I think the solution to this would be better coming from adjustments to the crime and punishment system to make sure there are meaningful risks/deterrents in place for non-consensual PvP encounters rather than from a binary PvP on/off toggle.
None of that even touches the concerns of a PvE player.
Those who don’t care to PvP could care less about adjustments to crime and punishment.
Being more specific…if I’m doing whatever (PvE), if my ship or now body/suit were attacked and damaged or blown up, that ruins my gaming experience. There’s literally no amount of crime and punishment changes that would fix or address that simple concern.
Perhaps I can offer other suggestions that would really make a difference.
1. Allow commanders to set specific roles for themselves when they leave a station which then enable or disable certain actions. Imagine a role of explorer that does not allow a commander to equip any weapons but instead is a pre-set of specific modules in outfitting for each ship.
Taking it further, someone who desires to be a pirate would be allowed to equip weapons, however, Fdevs would have to build a user interface where commanders with items on their ship will prompt each to accept or deny a request for goods. After such it either disables any combat if said commanders accept to give up goods. If they decline, then and only then does it allow the pirate to attack up until a ship drops said goods but does not allow the ship to be destroyed unless they fire back.
2. Another role could be a rogue or outlaw who does want to kill and destroy other commanders and other npcs. That role would attract npcs and commanders but freely be allowed to fire at will.
3. A role of passenger and goods transporter would not allow weapons but would allow other modules to sneak in and out of places.
4. Accepting X types of missions also would turn on/off roles so a commander could have more than one role at a time.
To me these are meaningful quality of life changes that would add depth and logic. I’m all for the game being for the elite and being dangerous but as it stands…it’s design encourages griefers and lots of other garbage.
lastly, private server gameplay should have a rule set for the host to allow or deny specific actions.