It would be nice if mkxf86config had synaptics support, so, now it does.
Created attachment 44657 [details, diff] Synaptics support patch
I incorporated your patch into the -gentoo patch, so there should be synaptics support. Please test the ebuild and let me know if it works.
Moving these so we can remove the "Install CD" component from "Gentoo Linux". I apologize to everyone for this spam, but according to the bugzilla developers, this is the only reasonable way to do this.