Instead of passing `"new_model"` to `translation_per_model`, you should simply pass `:new` as an action, and then internally do this:
```ruby
"#{action}_model"
# so:
I18n.t "active_admin.#{resource_class.to_s.downcase}.#{action}",
  :default => proc{ I18n.t "active_admin.#{action}_model", :model => model_label }
```

Note that this changes the behaviour quite a bit. That's because you shouldn't need to pass `:model` to the first translation, only to the defaul.