Hello.
I think you can do with a new different ways.
One way is just to set up a Send Port for each Partner with the correct transport type. The, use direct binding out of the Orchestation and route the messages to the correct trading partner based on SourceFileName. Just make sure you set up the subscriptions right otherwise you will get into an endless loop.
Another way to do it is to use Role Links. This way, you set up one Role for each partner. Then, you define a property to route your message to the Role (in your case SourceFileName). Then, you add the Send Port for the partner into the Role. This way you have a lot less risk in routing errors but you have a little more work to do.
Hope this helps.