Huh? Just set it after a set amount of idle time. I cant think why you would need a widget to start the screen saver. Is that not sorta redundant? I mean all the widget would be active with the saver running.
How about an apple script/automator action that you can link to in the dock. Click and it launches the script which start the screen saver.
I already stated I have all my hot corners assigned.
I use my screensaver as a way to lock my screen when I have to attend to something else. This is why I prefer to have an instant screensaver rather than wait for idle time. I'll try to mess with Automator.