True, and no one is suggesting Solo and Group are second class modes. But it's important to realise at the moment, using your logic, OPEN is a second class mode?
It's only fair to be realistic about the mechanics surely? Let's suggest Powerplay group A have to deliver a commodity to location X. Meanwhile Powerplay group B need to stop them.
As it stands, group A are penalised for playing in OPEN. They are rewarded (by less poweful/organised opposition) in non-OPEN - I don't believe this is a unfair assessment?
Except... no one is forcing group A to stay in open, if they don't like it there. Secondly, they get the added fun of interacting with other people (in a general sense) - isn't THAT what they are in Open for? This is how I understand the current mechanisms in play. If you want to interact with random people, feel free to do so in open, but don't expect the game to change. I.e. things will happen in the background, and there's nothing you can do about it. This goes beyond PP as well (quick example: trade, even without player intervention).