I can't see how there is any other option, without reducing crowds significantly, and they're not about to do that. You can build a new tier behind the other two, no reason why you can't extend the current second one in just the same way. The south stand was cleverly done, the north will be equally clever, just do away with corporate area between the two levels, and make it into seats.
I'm not convinced we need to change the dynamics of where the singers are again, its only one home game, but the signs on Sunday were very good that we now have an area full of people who want to sing. Keep the prices down, similar to the south, and we'll get back lots of fans who have been priced out too, and they will generate more noise.