It's two clicks - one to left click on the icon in the system tray, second to click on "Safely remove USB Mass Storage Device - Drive(
x" in the popup menu. I appreciate what you're saying about RSI, but it's only two mouse actions.
However, if you're transferring files using My Computer or Windows Explorer, you already have that open, and should be able to use the keyboard to highlight the Kindle drive, then press SHIFT+F10 to pop up the "right click" context menu, then arrow key down to "Eject" or "Safely Remove" and press enter.