Hmmm... 4 or 5 finger gestures on your 3.5" screen... No, I don't think that's a particularly good idea.
I don't even particularly think it's a good idea for the iPad. When you're in an app, your iPad becomes that app. System gestures that can take you out of that app are jarring and disconcerting and could well be triggered by accident. Plus it may well break apps that rely on 4 or 5 finger gestures.
The only system gesture on the iPad should be the Home button, which is off-screen. If I want to exit the current app, I press the Home button. Simple, clean, elegant, easy-to-understand. I don't think the masses are going to understand or want these "power-user" gestures.
64 GB iPad 2 WiFi, Apple TV 2, 32 GB iPhone 4
Early 2011 MacBook Pro 13" (dual boot with Windows 7), Early 2009 Mac Mini