Modifying blueprint for Content tab of admin panel?

For some pages on the admin panel, I'd like to remove the markdown editor and replace it with a different field. How can I both hide the markdown editor and add a new field via a blueprint?

FYI, I tried modifying the example which added a field to Advanced tab of the admin panel, but that didn't work.

Similar issue: I'd like to know how to edit the default blueprint or make a custom blueprint with an editor field that writes to the content section of a page.

Silly me, doing a text search of the Grav files not a filename search. I found the default.yaml blueprint and see you call the form field as 'content'. @philjms I suggest copying the default.yaml blueprint to your own user section and modifying it to fit your template requirements.