CMIS - Meta data bulk update

We have a requirement to update document metadata in bulk in FileNet and we are using CMIS service for that. Now, The structure provided by PEGA (CMIS-UpdateProperties class) only allows to update one document at a time. When we were discussing this with FileNet team, they provided us a xml structure where we can update multiple documents in one single call. That xml structure comes packaged with CMIS (it was not custom built for our application, it is OOTB for FileNet too), but it is not present in Pega. As all the CMIS request/response structure in PEGA is OOTB, so instead of consuming that XML, we are expecting PEGA to provide us that xml structure or any other alternate solution.