Can you create an External Content Type whose source is a WCF connection to a SharePoint list in a different farm?
For example, if a list exists in one farm (and is exposed through REST at http://www/_vti_bin/listdata.svc/OurList), can you consume that content with a WCF connection created in a second farm (http://teams/)?
The answer to a similar question suggests that it's not possible when dealing with "complex schemas". Can a standalone list be a valid source, or is it still too complex?