Strange discussion tbh.
In the Focused Feedback thread that Sandro started there appeared to be a clear majority of people who supported Open Only Power Play, and that included a large part of the people who actually engage in Power Play now.
In this thread I see quite a few who are against it because it would take away other players' choice, while the opponents themselves are not engaging in Power Play in the game as it is. I haven't seen a single opponent say "It would take away my choice to do Power Play in Solo or PG and I do that on a regular basis." So it appears that there is opposition based on a general attitude against any separation in the game, regardless of content.
On the other side there obviously are those who just want targets. Always have been, always will be. They want to shoot people and OOPP would give them an in-game reason to do it, without having to defend themselves when asked why they kill traders. "Because I can" isn't really a reason, it's an excuse. OOPP would be an in-game excuse, if nothing else.
So, it's obvious that neither side will budge, as the arguments on both sides appear to be based on feelings and general attitudes, rather than what's good for Power Play in the game. If that's what FDev listens to, they'll never be able to make decisions that are actually good for that specific content. It's like asking a player who only does PvP and has never left the bubble what should be done to improve exploration. Or the opposite, ask an explorer who has 8 different exploration outfitted ships, but none with weapons mounted, what should be done to improve PvP. Neither of them are good choices for good changes for that content.
To make any improvements to Power Play FDev needs to listen to the groups and players who actually do it, day in and day out. That's where the answer lies, not in this discussion or the infamous Hotel California thread. Whether they actually want to ask and listen is an entirely different issue.
For my own part I don't engage in Power Play, but I see the points from both sides. The only real gripe I have with going Open Only would be if the Power Play modules would remain in their current form. That would be gating of very specific content that I would have an issue with. So placing those modules behind another grindwall that is accessible in all modes would be a minimum requirement for my part atleast.