If you maintain your own code and your own templates as part of your policy package then inject the related code on your own either inside the related template or as part of the viewlet. We use a viewlet to inject JS and CSS specific to a policy package like this:
<script>
window.__define = window.define;
window.__require = window.require;
window.define = undefined;
window.require = undefined;
</script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++onkopedia.policy/spin/spin.min.js"></script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++onkopedia.policy/clipboard/clipboard.min.js"></script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++onkopedia.policy/uploadify/jquery.uploadifive.js"></script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++onkopedia.policy/jquery.qtip/jquery.qtip.min.js"></script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++onkopedia.policy/selectize.js/dist/js/standalone/selectize.min.js " > </script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++onkopedia.policy/jquery-ui-git.js" > </script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++onkopedia.policy/jquery.form-validator/jquery.form-validator.min.js" > </script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++onkopedia.policy/local.js"></script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++collective.glossary/tooltip.js"></script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++collective.glossary/jquery.glossarize.js"></script>
<script type="text/javascript" tal:attributes="src string:$portal_url/++resource++collective.glossary/main.js"></script>
<script>
window.define = window.__define;
window.require = window.__require;
window.__define = undefined;
window.__require = undefined;
</script>
For the resource registries...they are broken-by-design, having tons of issues. Yes, RR are still recommended by the Plone core developers but using them is error-prone, time consuming and usually it ends with a lot of frustration. Avoiding them altogether is the way to go for us.