Yes this would also be great. Though I will note one well received feature in my opinion was from version 19, where now Machform will check and auto-fix any malformed HTML in field labels. This was a huge addition for me, as I had users who knew enough HTML to bold, italicize and add links to their own field label or section break content.
But sometimes they were not stringent enough to ensure they had closed all tags properly, and then in past Machform versions that basically broke the form builder. Now that doesn't happen anymore, and it's great.
Still, I agree that a WYSIWYG, Rich-text or Markdown capable editor for field labels and section break values would most surely be a welcome addition and help bring Machform up to speed with other forms platforms out there.