The point of this workshop is not to teach people SMW interfaces. The amount of ground that can be covered in a one hour workshop aimed at beginners is rather small. So however this is done, people will still not know nearly all interfaces. So even if it was the case that this was likely to change, which it is not, I'd not see it make much of a difference. People still get to learn the workflow and they still get to learn how to find things out while creating an SMW extension, which is the whole point.
If you have a suggestion for something that is not a result format that could be created as part of the workshop, and that interfaces with code that does not prevent writing tests for the new code, then I'd be happy to hear about it. There is the Ask library, though that is likely to abstract for much of the audience.