I just tested on a project, it works for the general use-case 👏🏻.

In a specific controller, I modify the name of the template, to set a value from the routing config (a kind of custom TemplateController). The template is not rendered in the controller because there is some processing on the data between the controller result and the template listener.

use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template;
class TemplateController
    /**
     * @Template
     */
    public function templateAction(Request $request, string $template): array
    {
        $request->attributes->get('_template')->setTemplate($template);

        // Fetch data

        return [/* some data for the template */];
    }
}

This cannot be done with the controller attributes. Even if I could access the ControllerArgumentsEvent or the ControllerEvent, they provide access to the attributes, but do not allow update.

@GromNaN thanks trying and having a look.
The code now reads the _template attribute on the request. The attribute is not pre-populated because the listener reads it only after the controller is called, this means you can now do:
$request->attributes->set('_template', new Template($template))

Thanks you @nicolas-grekas, that's a great solution. I would add a test to prevent regression #46914

The same feature would be useful on other attributes.

I would add a test to prevent regression #46914

Thanks for the PR.

The same feature would be useful on other attributes.

That's already supported :)