I don't see how this would reduce complexity. If you don't need to scale, postgre still better enforces correctness and uses almost no resources. When you do need to scale, you WILL need to switch to postgre. Postgre is also dead simple to install and use for the "simple personal blog" use-cases. The enourmous technical debt you're taking on to reduce the one time installation by 2-3 commands and a slightly quicker download is not worth it.