Following steps 1 and 2 don't make my xsd modifications appear in the content assist. This is probably due to the fact that doing this does not actually remove the <name>org.jboss.tools.jst.web.kb.kbbuilder</name> builder.
If I close and reopen the project then the modifications show up.
I don't modify the xsd much these days so it's not a massive deal but, I was hoping it would be nice and smooth :)