Redundancy of ManifoldCF AuthorityServiceBaseURL

[Kambiz Niktabar]

Hello,
By looking at MCF Solr plugin and the configuration required in solrconfig.xml 
file, it seems it's not possible to have more than one AuthorityServiceBaseURL 
in solrconfig.xml to implement redundancy for document level security. So in 
case the MCF is down expanding user tokens can not be expanded.Can you advise 
what kind of workaround can be used to handle this situation?
RegardsKambiz Niktabar