An approach like this should work as well. One extra note, your runs might fail if you don't have any default value even when you're not using those items.

class ProjectHooks:
    @hook_impl
    def register_config_loader(conf_paths, env, extra_params) -> ConfigLoader:
        globals_dict = {}
        globals_dict["filepath"] = extra_params.get("filepath", "default_value")
        return TemplatedConfigLoader(
            conf_paths,
            globals_dict=globals_dict,
        )