I'm setting up an org that has a many-to-many relationship between "buyers" and "sellers." I'm using the Account object for both buyers and sellers and set the Type field picklist to have the choices "buyer" or "seller." Then, in order to complete the many-to-many relationship, I created a junction object called "Relationship" with two lookup fields: "Buyer" and "Seller." This works fine on the account level -- if BuyerA has relationships with Seller1 and Seller2, then the record for BuyerA has the relationship related list populated with Seller1 and Seller2, and so forth.
However, I want to be able to create a report that goes down to the contact level: For instance, I'd like to be able to have the report show all Seller contacts for BuyerA. So, if BuyerA has relationships with Seller1 and Seller2, and Seller1 has contacts ContactS1a and ContactS1b, and Seller2 has contacts ContactS2a and ContactS2b, the report filtered on BuyerA should show: ContactS1a, ContactS1b, ContactS2a, and ContactS2b. A further requirement is that the report needs to be exportable, so I can't use a joined report.
Is it possible to do this with standard or custom Salesforce reports? If so, how might I go about it -- I've tried every angle...custom reports, cross-joins, etc., but can't seem to get the results I need.
Alternatively, is the basic relationship structure flawed? Should I be using a custom object for buyers or sellers and not try to use the account object for both?
Edit: Here is a barebones sketch of the schema. And, if it helps at all to understand my situation, here's what the query for the report would look like in MSSQL:
SELECT c.* FROM Account a JOIN Relationship r ON r.BuyerId = a.Id JOIN Account a2 ON a2.Id = r.SellerId JOIN Contact c ON c.AccountId = a2.Id WHERE a.Name = 'BuyerA'