I also like the idea of a ballroom. The idea of dancing on a big balcony overlooking the city is enchanting.
My experience in other sims has been that what is absolutely [b:1mg9k8vv]crucial[/b:1mg9k8vv] is to have an [i:1mg9k8vv]events manager[/i:1mg9k8vv] and to have [i:1mg9k8vv]regular events[/i:1mg9k8vv], [u:1mg9k8vv]weekly[/u:1mg9k8vv] if possible to drum up traffic. This can seem artificial at times, but the minute the events stop, IMO the sim generally dies soon after. Also the presence of events can create traffic on the retail side where none normally exists.
If we don't do something really soon to get things started in the city, we might not have another chance. The addition of Nova Collonia (if it happens), can prop up our traffic numbers for a while, but we have to create a real economy and social life for this place or it will all end rather abruptly somewhere down the road IMO.
The Platz redevelopment can help in that way, but it is already a large open space that has little going on. Merely making it larger will not help. On a practical level, I see a problem in moving back the row of shops to the south as we would have to lower the little hill that the Museum currently sits on to do it and that would adversely affect the Museum. But even if we forget about that, we need to have a good reason for enlarging the Platz and [i:1mg9k8vv]concrete[/i:1mg9k8vv] plans for things to put there.
I would suggest that Rubaiyats coffee shop would be an ideal addition to the Platz as we all stand around and talk there anyway, having a coffee shop there would be a natural. As far as I understand though (and I can't really talk for Rubaiyat), there have been problems getting through all the red tape and discussion to get anything on the Platz at all. Perhaps instead of the auction of those lots (which now has to wait for the new layout plan), we could just prioritise the existing citizens and start [i:1mg9k8vv]concrete[/i:1mg9k8vv] plans for stores, coffee shops and what have you right now. Gwyn is waiting to move there as are others. Let's throw the rules away and just do it!
Another idea is to just set up some gypsy carts, "barrows" or stalls in the Platz owned by the city and rent them out. There are a lot of sellers in SL that only have five or six products and a low prim, low rent cart would be a good fit for some of these. They could be medieval in appearance, although I for one don't see why the products have to be.
Lets not get so hung up on our rules and our theme that we legislate ourselves out of business.
Remember we won't have the "drama-fuel" to keep us going anymore and to keep us in the public eye.