Aye no arguments about maintenance mind, that definitely needs improving.
Personally if we're going about improvements I wish they'd move the family area out of the South East corner and do a decent area for them with stuff that kids might actually want since they're the next generation of fans, ideally in an area of the ground which doesn't sell well ie. up in the concourse. Means you can give more space to the Roker end with them gaining the whole of the South stand.
Mind if you wanted to create more space in the concourse, one option could be to rip out half the bars and replace them with self service koisks, would create more space and you'd get a quicker pint aswell. I know you'll get the usual lot moaning about machines and refusing to use them nonsense but for the vast majority of people it would be better really.