This is such a simple request yet it seems impossible for Evernote to deliver on.
I've tried other workarounds, such as:
Duplicating a blank note where I've set the custom style attributes, but the customizations do not carry over to the new note.
Creating a custom template, and loading that template when creating a new note. Doesn't work either.
Even if the above solutions worked, it would also work for new notes and not past notes. There should be a feature to import/overwrite style, similar to how any MS Office product uses style sheets.
But I have gotten on solution to work which is completely external from Evernote. I've created a keyboard and mouse macro to customize the changes I need. This is a little tricky as you need to first have the macro position the Evernote window so that your mouse movements are accurate on an X/Y screen axis.