Multiple ResourceFilters

[Marvin S. Addison]

We're working on refactoring our IdP configuration and we'd like to 
distill environment configuration in two properties files:

1. Information common to all tiers
2. Sensitive information specific to a particular host/tier

The service.xml snippet to go with:

<srv:ConfigurationResource
         file="/opt/shibboleth-idp/conf/attribute-resolver.xml"
         xsi:type="resource:FilesystemResource">
     <ResourceFilter xsi:type="PropertyReplacement"
                     xmlns="urn:mace:shibboleth:2.0:resource"
                     propertyFile="/path/to/idp.properties"/>
     <ResourceFilter xsi:type="PropertyReplacement"
                 xmlns="urn:mace:shibboleth:2.0:resource"
                 propertyFile="/path/to/idp-env.properties"/>
</srv:ConfigurationResource>

Unfortunately it appears that the resource schema allows exactly one 
ResourceFilter element:

     <complexType name="ResourceType" abstract="true">
         <sequence>
             <element ref="res:ResourceFilter" minOccurs="0"/>
         </sequence>
     </complexType>

Am I reading that right? Assuming yes, has anyone created an extension 
to provide support for multiple resource filters? If there's no such 
beast, would anyone hazard a work/difficulty estimate on developing that 
functionality? At first glance 
https://wiki.shibboleth.net/confluence/display/SHIB2/IdPExtResFilter was 
a little intimidating for something so seemingly simple.

Looking at alternatives, could I leverage the Spring beans schema to 
wire up a PropertyPlaceholderConfigurer which naturally supports 
multiple property file locations?

Thanks,
Marvin