I propose adding the Link (Synchronize) action to the Visual editor next to the Preferences, Refresh, Page Design Options actions.
This action would be a check box similar to the "Link with editor" in the Package Explorer view. It would be checked/enabled by default. In that case, the VPE would behave as it does now. If the user disables the action, the VPE wouldn't be updated (VpeController.notifyChanged() wouldn't be called). This would be very useful when editing large JSP files. The user could always call Refresh (or check Link) to show the visual part of the editor.