Can Anything Other Than An Image Be Used In Custom Toolbox Items

I have developed a renderer that renders the xml to paint a rectangle with textboxes in all the right places based on the data retrieved off the database. When i render the a complete report to the reportviewer i have no problem.

I need however to render the rectangle into a custom report item for reusability and different scenarios. This just seem to be impossible since it seems like I cant use anything other than an imagemap to render custom report items. Is this true?

To make sure you understand....in other words....

Is there a way to develop a Microsoft.ReportingServices.ReportRendering.IRenderingExtension that renders the required xml like rectangles/textboxes etc. and then migrate this to a custom toolbox item. It just seems like this should be a very easy thing to do and something regularly needed. For example when you want to use textboxes in certain positions within a rectangle to draw a organisational chart.