I slammed this plugin into a site I'm developing:
I was looking for a way to allow a user to add a featured listing to their sidebar, not necessarily a Real Estate plugin.
Other than spending waaaay toooo much time customizing the widget, it is working pretty damn good.
After reviewing your wish list I can only say, you have really bit it off. I hope somebody gives you some money or other incentive to keep it going. Moreover, I hope you have a good vision of where you want to go with this.
How active on the forums are you?