I'm not looking for "dynamic" as in realtime changes, page-load is fine. Enablement is based on installation/use of other plugins. Here's what I've got together now as a workaround:
<f:entry title="${e.id}">
<j:choose>
<j:when test="${e.disabledText != null}">
<label tooltip="${%Not applicable}: ${e.disabledText}">
<input type="checkbox" disabled="disabled"/>
${e.description}
</label>
</j:when>
<j:otherwise>
<f:checkbox title="${e.description}" name="exclusions" default="${instance.exclusions.contains(e.id)}"
json="${e.id}"/>
</j:otherwise>
</j:choose>
</f:entry>