It would be funny if Daiya's wish caused another time loop, just like in Mogi's case.

I expect there is going to be some way to get her memory back, but maybe not. Either way, I don't think that would break Kazu's resolve at this point. Even if she doesn't know who he is, he'll still want to free her from the endless cycle.

It was unclear to me whether Flawed Bliss was actually Aya's wish when she died, or if Maria somehow made this wish. Since O is created from the wish, I hope we'll get some kind of explanation for where the initial wish came from.
Even with her memory wiped, Maria is still trying to be Aya, so I don't think this really counts as the Zeroth Maria.

The most interesting character so far has been Daiya, so I hope we'll see more of him in the final volume. I also thought Iroha was pretty interesting in the Game of Idleness and also her role in Daiya's master plan. She didn't do anything in 6, but I wonder if she can recover.