Mosaico has an updated version of the versafix template -
What is required to add/replace the current versafix with this updated version?
You can check out the version from github repo and place the template in your installation. I have just cloned https://github.com/voidlabs/versafix-template/tree/v1.1.19/dist/template folder to my Mosaico templates folder and it works.
You can copy the folder as versafix-new and rename html file as template-versafix-new.html so your legacy copy wouldn't get overrided.
p.s. The blog post was about 1.5 years old so my answer is about 1.1.19 instead of 1.1.16.