Hi Steve,
I'm not certain that dynamic updates to HTML in the <head></head> section of the page are supported by browsers .. they tend to parse/act on that area of the page when it's first loaded, then not 'worry' about it until the full page is reloaded.
If you look at the HTML spec for <title> it's just bare-bones with none of the attributes available with a <span>, <div> or <p> tag.
So.. it's unlikely that dynamic changes to <title> will be work as you wish.
Best regards,
Ken