I don't know if someone else has posted or thought of this.
Make a APK, ROM, or kernel to support the hard key backlight as a flashing LED notifier.
Good idea, but in the interim you may want to try the NOLED app from android market. It's free and works beautifully on my Charge to notify me of e-mails, missed calls, SMS messages, etc.
Samsung Galaxy Note 3
Stock ROM (JB 4.3) -- awaiting KitKat