This can be achieved with the editor styles coming to 2.0! (Which can be tested in preview now.) I totally agree with you — so I did that exact change in my first attempt at an editor style.
Here you can see a screenshot:
Is something like that what you wanted? 
Installing them are a bit complicated at the moment, but Jesse has written good guides for how to achieve it. And if you want to try out my style, it’s linked on the link above.