I've been told that the best chance of getting this extremely important and basic feature added is to have people up vote this on the forum. As unsatisfying as that response is, please upvote the linked topic.
I had a look and this is not possible at this stage with HubSpot. You could use a personnalized Snippet in the body of the email with those properties, but not in the email subject field.
However, I could see it could be useful for you and other users and I'd recommend posting an Idea in our Ideas Forum regarding this. That way other users can upvote it; and the Product Team regularly monitors the Forum - I couldn't find a similar idea for this.