I do know there is an option in KUAL to make the store button launch KUAL instead, and a separate way to change the icon to the KUAL icon. The same concept should (and possibly does, on Goodreads-enabled devices?) replace the "g", although I don't think you can make it disappear.
People have also changed it to launch the browser.
None of this matters for the KT2 or KV, until a new jailbreak is discovered that does not involve the serial port.
I highly doubt the firmware itself will ever let you customize it though.