Hi Mike,
its interesting to know, that the BSP-copy of the swn_message1 could also be a common solution. I've done so only once by now, and I was in need to make some changes on the layout with additional information.
If you need to change more than then layout, you have to subtype the controller-class, too, and basically overtake the complete processing in the do_request() method... which is a large spagetthi-code, so you can't just subtype some (other) protected methods to just make some variations. It means either: Do everything manually yourself, or leave it as it was.
With that experience in mind, I now just leave the template as it is ... as much as I can.
But you're right, the solution might be indeed, that a copy is just required.
I have no customer OSS-account with what I would be able to raise a message :-(
With the very best wishes
Florin