Am I understanding right that you’re trying to use a module to swap out the template being used? What event are you trying to listen to for this? I would suspect that the Omeka-provided “view.” events wouldn’t work, since they’re all triggered within the view files themselves, so if they are triggered then we’ve already started rendering that view with the original template… though maybe you could make that work if you rendered to the “current” view model instead of a new one.
Instead of doing this, you might try listening to the Zend-provided “render” event… you could attach right before the default listener there and just change the template in the view model at that point, just before the actual rendering starts.