I'm a little iffy on this idea, and here's why:
Once hardware is supported, it generally stays that way. This is not so for unsupported hardware. Being that there is a LOT of hardware that we still wish FreeBSD supports, this list could grow to an enormous size, and would thus be difficult to maintain when updating the list (from unsupported to supported).
A list of supported hardware might be a good idea, but the release notes seem to have this area covered.
Perhaps a forum or sticky thread for requested hardware support is in order? That way it is possible to know what is in demand.