I recommend you contact freenas and send them the following link which is a search of the PFSense CVS timeline for ALIX. It lists the changes needed to make m0n0wall and PFSense work with the ALIX board.
http://cvstrac.pfsense.com/search?s=alix&t=1&c=1
Other than that you could suggest to freenas developers to chat with PfSense developers so they can get the changes necessary to make it work on the ALIX board.
More collaboration between FreeBSD, PFSense, m0n0wall, FreeNAS, PC-BSD, DesktopBSD and Askozia will help make everyone of them better. In fact I think as PFSense, m0n0wall, FreeNAS, PC-BSD, DesktopBSD and Askozia become more popular I think FreeBSD itself will be improved and become more popular.
Best Regards,
Mark