I know this probably isn't the best solution but I'm going to put it out there anyway.
I've done something similar to this using .Net's System.ComponenetModel.DesignSurface. This is the same design service used in Visual Studio's Windows Forms so all you do is create your controls, add your control designers if you want and you're good to go. You can use the PropertyGrid to display the data for each object as they are selected. Code Project has several articles about this like this one.
That said it's not going to be the best performance wise, I've got several thousand controls on my DesignSurface in some cases and it gets sluggish. You may be able to get around this by using another root designer type (WPF maybe?).
This could be a very good option if you already know how to do custom Windows Forms controls. And best of all it’s free!