The following standalone.xml entry:

<server>
...
    <system-properties>
        <property name="test.acme.conf.dir" value="${jboss.server.config.dir}/acme"/>
        <property name="test.acme.data.dir" value="${env.PWD}/../standalone/data/acme"/>
        <property name="test.acme.db.dir" value="${test.acme.data.dir}/db"/>
    </system-properties>
...
</server>

produces the following system properties:

test.acme.conf.dir=${jboss.server.config.dir}/acme
test.acme.data.dir=${env.PWD}../standalone/data/acme
test.acme.db.dir=${test.acme.data.dir}/db

I would expect property references to be resolved - i.e.:

test.acme.conf.dir=/opt/jboss-as-7.1.0.Final/standalone/configuration/acme
test.acme.data.dir=/opt/jboss-as-7.1.0.Final/bin/../standalone/data/acme
test.acme.db.dir=/opt/jboss-as-7.1.0.Final/bin/../standalone/data/acme/db