From what you describe I don't think Proc Metalib is what you're aiming for.
Proc Metalib synchronises physical SAS tables with Metadata definitions for SAS tables.
Metadata contains only data about data - in the case of a SAS table the metadata would be things like: In what library is the table, what variables with what formats, informats,... are in it, etc.
Therefore something like a "dataset on a metadata library" can't be; there is only a metadata table definition pointing to a physical SAS table.
As long as you can access the physical SAS table directly (libname myds 'path where target SAS table is stored';) you can ignore the metadata at all for what you want to do.
HTH
Patrick