The grammar for tagged expressions is relatively complicated in comparison to this, so it might be better to wait on that. I think getting template literals working correctly is much simpler and would be a great first shot at this, maybe subsequent patches could add the additional logic for tagged expressions.

That said, if support for some rudimentary tagged templates is really necessary, I'll have a go at adding that in in the initial patch. But given the relative complexity of the tagged templates, I think it would be more of a challenge to alter or roll it back at a later time if necessary.