I've actually had another idea since the deadline, drat. It might be a bit of a controversial one as people first look at it, but I've been thinking on the success of the layout of parts of Hindmarsh square and how they mesh with their surrounds because they are not isolated by traffic around their perimeter.
The ideas behind it are:
1 Through traffic is a reality, but tunnels are not possible due to the long run ups required.
2 For people to make daily use of it, it really needs to mesh with the surrounding buildings, be an extension of the activities at its perimeter.
3 To be a useful and functional space for special events it needs to be a large contiguous space.
Obviously points 1 and 3 are not compatible, unless we allow the roads to be roads most of the time, but close them off for events. To this end I've eradicated the diamond, there are no access roads at the perimeter (except a provision to allow taxis and dropoffs access to the Hilton's front door) instead KWS and Grote/Wakefield bisect the square on both axes. However they are not normal black top roads, whilst in the square they are differently paved roads (possibly those high wear pavers that they use in shared zones in Germany) the kerbs are also removed and replaced with flat style spoon gutters (like in Rundle Mall) in order to provide a completely flat surface. In this way the entire square can be cordoned during large events without anyone tripping over the gutters etc.
I was toying with the idea of a shared traffic/pedestrian space in the orange zone - but haven't convinced myself that it would work as yet.
Also I have the idea that the intersection in the centre of the square could be mounted by some kind of spire or other architectural feature that is accessed from the supporting pillars at each of the four cardinal points (NE, SE, SW & NW) around the intersection (the red crosshatches and the green blobs). Perhaps even providing a pedestrian overpass to the tram stop?
Additionally certain buildings around the perimeter would be allowed to 'invade' the square to small degrees. An example might be an extension of the Central Markets Arcade or if the Law Courts become a shopping centre an extension of their entry to accommodate outdoor cafés etc. Perhaps a low rise cultural building of some sort could be constructed in a corner for whatever purposes can be thought of.
The green areas would be landscaped in such a way that would facilitate the best balance between the daily functions and the special events functions.
Here's a really rough sketch I made with crayons in my lunch break weeks ago... *shame*
I stress it's a really rough sketch, I was just jotting down the idea before I forgot it. And it's a really rough outline of where I was going with this before I changed jobs and lost my life.
Do with it what you will.