What about something along the lines of renderers? Renderer is not quite the right name, and neither are Producer / Provider / Supplier. TooltipContentBuilder?
I'll continue with the renderer name for the example below.
Create a TooltipRenderer interface which would be used by the ComponentSkin class.
Something along the lines of
public interface TooltipRenderer
public Component render(Object component, String tooltipText, Object tooltipData);
Add a tooltipRenderer property to Component
Add a tooltipData property to Component to give as much freedom as possible to developers (or just replace tooltipText)
It would be the responsibility of this renderer to supply a Component that will be placed into the tooltip popup window.
A default implementation might just create a Label and set its text to tooltipText.
A custom implementation would be free to generate whatever graph of components it wanted. It could gather data from the Component parenting the tooltip and/or from the tooltipData object.
This could be the basis of
This could also be taken further to combine tooltip show & hide delays, specifying transitions, rate & delays to create a TooltipPolicy.