I am working on a 1.1 GUI design tool that works with Components using the
1.0.2 event model (handleEvent). During the design mode I would like to
listen to Mouse events on a Component (addMouseListener), but this permanently
breaks the old event model propigation even if I call removeMouseListener before
entering test mode.

The 1.0.2 event model should work if no listeners are registered on a Component.
Looking at the Component.java code, I see that the newEventsOnly flag is set
when listeners are added, but it is never reset if all listeners have been
removed.