I'm in what I think to be a minority but I think the way to fix City Hall Plaza is to tear up the brick and add more grass and trees. Then host more events like big shows and call it a day. I have personally enjoyed a number of festivals and events there, including watching the world cup on a huge screen with thousands of other people. I think it's important for cities to retain this kind of public space. The fact that it's a barren wasteland that feels like crossing a desert in the summer or the tundra in the winter can be fixed. We can never get it back if we build over it.
And the seawall, eh. As long as it's a green sponge and not concrete then knock yourself out.