I have been behind a PVE option in the menu for a long time, I play in open, group or solo as my mood dictates.
Mobius is one of the groups I play in so why would I be behind a PVE group? because > 93%* of game owners do not have a forum account, of that ~ 6.2%* we have been told by Brett follow the general rule of active vs posted once, I think he said it was 90-9-1.
If people don't use the forums its highly unlikely they would have heard of Mobius, a PVE option at login is hard to ignore, its all about choices.
I get that the open PVP people that like non consenting PVP would be worried open would lose players, on the flip side the PVE option would likely include many more than are in Mobius (or fragmented in other PVE groups), it may even get some solo players to try it, (there are some that never will, they bought the game as a solo game and fair play to them) but I think a PVE option would be very popular (Mobius > 11k now).
The idea I am behind is a mirror image of Mobius, run by FD with triggers? I think they were called earlier.
Click on PVE, get the message "You are about to enter PVE mode, you agree that 1) if you attack / kill another player you will pay the full cost of the damage. 2) you will be banned from the PVE group
for ever (account not CMDR). 3) you will be fined 50% of your total wealth (not cash) and that amount will be put on you as a bounty for the next 6 months (and you are forced to play in open, or shadow banned for 6 months).
Mobius had to kick 6 people in a year, 2 were code kidiots in one sitting, I don't think there would be a massive problem with PKing in a PVE group after the first few "I quit ED sucks, you actually did it!11!!1" threads, plus FD have all the info and could automate a lot of the management e.g. victim automatically respawns in PVE in the same place they got killed with everything they had, the killer gets booted to open with the bounty or shadow banned.
That said I am starting to think I might even be OK with the other option, disable fire against other CMDR's. I don't like to talk about immersion but it seemed cheap to me, but one would hope even in 2015 military aircraft would have an IFF system that would ask the question "do you really want to fire a missile at a friendly jet, are you really sure?, so by 3300 maybe.
* 850k copy's sold 52719 forum members
https://forums.frontier.co.uk/memberlist.php
TLDR I would take any PVE option in the menu for all the people out there that don't realise its a choice in the game.
There are some that would like to hide this option from the large majority or the players for their own personal reasons, not the good of the game or its population, I ahd better stop right there.