I don't want to spam this topic, but I've found another possible solution -
Currently the webapp has the following in its jboss-web.xml file:
<class-loading>
<loader-repository>
myapp.com:loader=myapp.war
</loader-repository>
</class-loading>
when I remove this, the application works with the multiple Qnames, problem is that off course this loader-repository option is put there for a reason - the application is installed in production together with a much older ear. Withouth the above everything explodes...