I noticed you wrote the following:
"My question is, when I move the files over to a CIFS share on a filer, in order to maintain the ability for the group to manage the files, I need to make them members of the local Administrators group on the filer itself"
I d suggest to you that the storage admins should not have to do CIFS permissioning. In most big evnironments I have been to its not seen as secure nor scalable to have
the storage admins doing CIFS permissioning.
The way I have seen this been done in the past is that the storage guys create a cifs share wide open, then its grabbed by the windows team that will set permissions and
deal with any issues. After all the windows guys will have access to AD admin accounts and thus will be in a good position to fix any issues. They will also have the
knowledge about how permissions should be fixed to fit current security requirements etc.
My two pennies worth, which would void having to deal with your current issue.