Ok, did a lot of Spec-Readup over the weekend, and yes EAP7.1 is spec-compliant (CDI and EE) while EAP6.4 was a little too relaxed on spec-enforcement.

In short - bundling the jars into the Ear, mentioning them as <ear>-Modules in the application.xml did the trick. Some naming confusion after that (Bean name is ambiguous) but enforcing strict classloader separation did the trick.