I´m not against the idea but I could try:
1. Sure Open PvE would have much more people flying around, but some (inviduals/groups) go to their own mode for their own privacy.
Huge Milky Way also would pretty much ensure that even in Open PvE group player encounters would be more or less random and rare (besides few known/temporarily popular systems for players), also divided to 4 instead of 3 groups might harm players online-numbers in all of them, not all Private/Solo moders would get to Open PvE, if even most (though I doubt it would hurt Solo or Private Groups a bit, but from that we come to following below).
2. and 3. contradict each others, would it affect numbers in Open or not?
But you are right in 4. that many explorers especially would still stay in Open (no risk almost at all but that slight possibility of running to somebody dangerous middle of nowhere..), and there are some traders who would feel bored without added risk from Open (because npc pirates could not even Hyperdict or catch after that a cow with rocket pack and a space helmet).
To your reply on #1,
I will partly agree with you, but it's the private groups that would suffer, not Open.
Honestly, Open play wouldn't be affected much inho, I think it's the private groups that would stand the most to loose, some could even cease to exist. But the reason those group do exist is mostly out of an attempt to work round this very issue. Most of those players wouldn't be quitting, they would have migrated to the PvE mode. I think it will be a net gain in the end, as more people would be in PvE mode then any other. New players would fill in PvE Play and PvP Play over time.
Private groups would become just that, small, specific purposed groups for a specific task, like racing or other event oriented things where the runners want to control the crowds. Here's a really good question, Is that what FDev really meant for private groups to be? If so, even if the large groups collapsed, there would be a much overall larger area to find more commanders to play with in net total.
Solo is unaffected. 1+0=1. Could solo players be drawn out into PvE mode? Some might, and that would be an absolute net gain to make up some of the difference.
As for 2 & 3....
Those were kind of pulled out of context form their original paragraphs
(By me). Point 3 was really trying to say that many PvP'er argue that the game is already too easy, and any suggestion with even the slightest amount of QoL often triggers them into complaining that the game is easy enough.
Anyone in Open PVP is fair game with no more excuses to complain about PvP. For the PvP community, they themselves would have a place where they can meet like minded individuals. Kill or be Killed will rule absolutely with no excuse. Thus why it's worded wild wild west. Each blip on your scanner could be a CMDR who's gonna just fly by and o7, or that CMDR might just hunt you relentlessly. For those who like that high stakes flying, people will play it for that challenge alone. Game on!
Anyhow, to your point...
Is it possible the numbers could drop in Open, I will concede the point, perhaps a little bit. But it would end debate and the bullying. In some ways, it seems to be a side effect that the game design pushes the PvE community who don't want to play alone onto PvP players.
Two communities that don't see Eye to Eye are forced together, for the appearance of a vibrant world. They force a larger peaceful majority into an area with a more aggressive minority for the sake of 'content'. Then they punish that majority should they not like it by making them play in limited modes. That's really what seems to be going on here. This has led to bullying and frustration for many, and even hate. Not the best game design for a deep space exploration game. IMHO
One final factor is the people who just want to watch the world burn, the Gankers of the Galaxy. None of this affects them. Ironically, they'd go to the PvE mode to harass people, more likely because they are less likely to get shot. [big grin] Nothing is going to stop them, but, depending on how the mechanic of a PvE mode would work, it at least prevents them from ruining hours of play by another player just for kicks. The revamped C&P system of 3.0 won't really affect them. I saw it in beta, it won't help.