For the longest time I only played in open, but in recent months I've played a lot in Mobius private group because the majority of players I know are there and I have to be in the same group to interact with them.
I think an extra play mode *might* formalise things removing the need for a Mobius-style PvE group, but what is more likely to happen is the fracturing of the online community, some in open, some in private and some in open PvE; and never the twain shall meet. Not something I'd want to see happen, so I vote no.
I'd rather see PvP & piracy more formalised. So it has enforced rules and PvP itself could only be consented to, in a game context, not inflicted (no space ). This could then be followed with strict policies on combat-logging (e.g. a three strikes rule).
This would then see MORE people in Open rather than less, which is where we want to be.
What could those rules be?
Piracy: Pirates when buying a cargo-scanner get a new COMMS button "Hand over cargo". Which when enabled (by using scanner on target), sends the message to trader. Trader then has 15 seconds to hand over 1 to 146T of cargo (based on approx. 20% of total) or become fair game. Zero cargo = can't send message. Attacking without making warning results in massive federal response (ie. - seven police Vultures or three police Anacondas) against the offending pirate.
PvP: Unless a commander is Wanted, a PowerPlay Enemy or in a CZ (or power-play equivalent), both players must issue challenge and response to consent to PvP, or attack on clean player will result in massive federal response (almost certain death) unless in an Anarchy system, where all bets are off.
Combat Loggers: Logging out during combat is locked to 15 seconds before quit already (we've all had the doorbell go etc.) but the odds against it happening more than once a week? Slim. So, you get a 15 second log out once a week. Use it wisely. After which you cannot log out until safe or dead. If you combat log or get disconnected by hardware failure, the server records a "strike". Get three and your ship blows-up in your absence. You'll come back to a rebuy screen. Firm but fair. If you are having network or hardware issues, stay away from combat. If you are wanted, you can no longer CTRL-ALT-DEL to escape more than three times before losing it all. Again the clock should be reset, but for a longer period (i.e. three times in a month). Your CL "strikes" should be visible in status right beside the rebuy.
With strict, fair, transparent rules in Open, there's no reason why everybody couldn't play there and be happy.