Not a premium member myself, but isn't that what the new analysis board is in live chess? Don't know what's available for turn based though. . .
Option to critique opponents game?

Ah. Well, in that case I would suggest either unrated games where you talk to your opponent in the chat section, or maybe once you get to the end of the game, quickly play it in live chess then use the analysis board? Again, I only have a vague notion of how the AB works, so I could be wrong about this.

Well, I know people probably don't want to hear suggestions during their games. They might even get mad or annoyed and some could see this as rude behavior (to be given unasked for advice.)
Not familiar with "live chess" just yet.

Well I was assuming that you meant that you'd be playing an opponent who was aware and accepting of the mutual criticism thing while playing turn-based, and then you could challenge the same opponent to a live game, play the same moves as in the online game (again unrated) and then use the analysis board to look at earlier positions/lines/whatever. Of course, if you just want people to do constructive criticism on a game that's already over, there's a whole forum for that http://www.chess.com/forum/category/game-analysis
How about users having the option to choose to be criticized (constructively, of course!) and open to suggestions (for improvement) from their opponents, during and or after a game? If you want to be open to suggestion, choose to be and if not, you can opt out. And this is a suggestion for "Online Chess".
It will get people to discuss the game more and help everyone with their game.