Idoc ORDERS05 with Custom Message Type

We want to use a Z message type for idoc type ORDERS05 to be able to separate a particular group of partners from other partners using ORDERS/ORDERS05.

The goal with our Z message type is to use the standard function IDOC_OUTPUT_ORDERS. The only problem I see is that this function checks the message type in form READ_SERVICE_PACKAGE. It would ignore this code since my message type is a Z and it's checking for message type ORDERS.

I was thinking of using a Z wrap-around function to perform the same code in form READ_SERVICE_PACKAGE if the message type is my Z message type.

I want to avoid creating a Z copy of IDOC_OUTPUT_ORDERS and all if the includes!!!

Any suggestions?