Madwifi ath0 uses a virtual address so macchanger doesn't work on it, you need to destroy the interface, change wifi0 mac, and create a new ath0. See eg. http://www.securityfocus.com/archive/137/467747/30/60/threaded http://www2.informatik.hu-berlin.de/~pilop/HOWTO_Gentoo_T43/
Not applicable to the macchanger tool itself. The baselayout macchanger wrapper needs the changes.
Base-system it is then.
macchanger baselayout script won't do this as already pointed out, ath0 is a virtual interface. As each virtual interface as a different way of being created it would be too much work to code the macchanger script for every one. You can use udev rules if you like.
