When trying to make a link from an overlay to a JAR, classes from overlay libraries are not loaded for a linked JAR.
The situation is similar when creating a link to a JAR which is located inside EAR.

Should overlay deployment mechanism be supported for JARs?

Example standalone.xml:

<deployment-overlays>
...
    <deployment-overlay name="my-overlay-n1">
        <content ...>
        <deployment name="my-jar-inside-ear-use-overlays-libs.jar"/>