You can use multiple Data Adapters in the same session, as demonstrated by the various demos included in the distribution package.
Hence, for each table, the client can specify one Data Adapter, to which all items in the table belong.

However, a single Medatata Adapter must be used.
Unfortunately, the authorization requests to the Metadata Adapter don't specify the Data Adapter name, so you have to supply items with different names from different Data Adapters and you have to base on the item names only in order to authorize each request in the way required by the related data source.

On the other hand, you can't perform multiple authentications in a single session. You would need to find some compromise.