The few SharePoint Records Management resources Microsoft has made publically available all suggest limiting Records Libraries to one unique Content Type each. In other words, all of an organization’s contracts will be declared to the ‘Contracts’ Records Library (and, presumably, given the same retention). As experienced Records Managers, we know this simply isn’t practical. Rarely – if ever – will a single file plan component contain just one record type. This is certainly true for case-based records management, where a whole array of different record types are routinely maintained in the same folder.
I believe Microsoft promotes the notion of one Records Library/one Content Type because they want customers to use the Records Routing functionality that installs with Records Center out-of-the-box. That’s understandable and I also believe in using the Records Routing tables, but one Content Type is just not practical for real-world implementations. 
So how do you manage multiple record types in the same Records Libraries? Here’s how one of my customers is doing it. First, create a single content type for all of your team, department or organization’s records. Call it ‘Accounting Record Content Type’ or ‘Acme Company Record Content Type’. Make sure the Content Type includes all the attributes necessary to manage the record throughout its life cycle. Assign the Record Content Type to all of your Records Center Libraries.
Next, have your developers customize the records routing process to route documents to the Records Center based on metadata value’s assigned to the original document’s Content Type. (I’ve discussed metadata-based records routing in several previous posts.) Now when your users declare the Elm Street Bridge Project contract a record, it can go into the ‘Elm Street Bridge Project’ Records Library with the other project related records, regardless of its Content Type.
To make this process even more efficient, I suggest including all the Record Content Type attributes in the base Content Types of all of your organization’s document Content Types and have your developers migrate these values to the Record Content type at declaration. That way, when your users create a document, they can fill out the necessary record information from its inception.
