You need to lean a RichFaces basic more. Supporting properties of something is not a job for a4j:support. a4j:support allows to work other component as they work, but in ajax mode.
In your code snippet, wrap the first h:selectOneMenu with a4j:region.
Read about it:
and here: http://www.jboss.org/file-access/default/members/jbossrichfaces/freezone/docs/devguide/en/html/region.html
P.S. The best version to working with JSF-RI 1.2 is RichFaces 3.2.1
Yes, you're right, after a few hours of reading I got it.