Problem: inspired by demo DB I usualy make one custom control with application layout component. Its visual style is shared through every page in application, what is perfect.
But on every page there might be something you want to show differently. For example Search options. Or content of Placebar area. I am talking about tree style properties.
Required feature: to define my custom control's parameters and use them inside application layout control (configure it using compositeData.param script). This is not posiible now, AFAIK.
Known workaround: use bean. This is not very useful - you would need set of dedicated classes for every page. :-(