With the new modules structure, Multi-JSF is looking for JSF implementations in the root of the modules directory instead of in modules/system/layers/base. The reason is that Multi-JSF relies on the module.path property which points to the root by default.

The workaround is to go ahead and install the new JSF impl wherever you wish and add that directory to JBOSS_MODULEPATH in the startup script.

See https://community.jboss.org/wiki/DesignOfAS7Multi-JSFFeature#comment-11789