There is a way to do this in the theme. But the action is not on the photo it is on the employee name below the photo on the front page. What I have found in setting up my employee pages for the front page is that there is a place to add a link to a second post that can contain an employee bio.
When you are under the special employee section under the dashboard and you are creating your employee “summary” go further down the page to the employee section and below all the social media links you will find “Custom link - Add a link here if you want the employee name to link somewhere:” and then there is a field to into the link or page slug for the full bio. Fill that in, resave the page and the front page employee summary should link to the full employee bio page.
For me that means I have had to develop a short-hand way of naming the different posts for employees as I have done all the employee descriptions within the employee management section of the dashboard (2 posts for each employee). So I have used nicknames for the headshots & social media links and full names for the full biographical posts. I have also added “biography” to the page titles/slugs for the full narrative backgrounds.
to see it in action see: http://shogrenconsulting.com
Hope this helps. And I agree, it would be great to get the link on by hovering over the image.