I've done this plenty of times. It pains me that I have to modify the footer on 5 different pages if something changes. I want to separate the content from the design, but I dont want to use databases. And I want to use ready-made templates that work well in different environments.
You can accomplish what you want with a good template from ThemeForest (or anywhere else) and some Server Side Includes or a dash of PHP if you are in a time crunch.
But if you want to edit in Markdown, a static site generator might be worth looking into.