I would not recommend the Save as Draft approach as I don’t believe it will help you accomplish your ultimate goal. WordPress is saving revisions in a non-public Post Type (more info here).
I found a “Changelog” plugin, which may help track changes to existing blog posts. You can see that here https://wordpress.org/plugins/awesome-changelog/.
Finally, a stock WordPress approach may be the following:
Publish a blog post and create a unique tag. For example, if your blog post is called “Hello World,” then name the tag hello_world_revisions. Then, when you are ready to revise the post, create a new post, and call it “Hello World.” Tag it with the same hello_world_revisions tag, and that way, all of your revised blog posts are tagged the same, and you can direct your users to that tag when you want them to explore older versions.
There are also other ways to accomplish your goals, but they would require custom code and custom theming. The items noted above are a quick, non-programming way to get started.