or for an action to have more than one resulting template.
I'm not so sure about this. I would either make the template flexible enough to handle everything the action needs, or to create two different actions
But how do you know what action is going to get run, then?
See my example about form validation above. Basically, you recieve data from "form 1" ( to an action) , and you want to either a) go back to a form 1. b) proceed to form 2, and try to submit that (repeat for form 2, 3 etc.).
In your system you will need to include form 1 and form 2 into one template just because the action can't choose the template for you. It's certainly possible to do that, but I think it will get ugly very quickly.